diff --git a/core/lib/Drupal/Core/Form/FormState.php b/core/lib/Drupal/Core/Form/FormState.php
index c37269a..b15eb38 100644
--- a/core/lib/Drupal/Core/Form/FormState.php
+++ b/core/lib/Drupal/Core/Form/FormState.php
@@ -1212,7 +1212,7 @@ protected function moduleLoadInclude($module, $type, $name = NULL) {
   /**
    * {@inheritdoc}
    */
-  public function getFormStateForSubform(array $element) {
+  public function getSubFormState(array $element) {
     return SubFormState::createForSubform($element, $this);
   }
 
diff --git a/core/lib/Drupal/Core/Form/FormStateInterface.php b/core/lib/Drupal/Core/Form/FormStateInterface.php
index a396440..1ac1e6d 100644
--- a/core/lib/Drupal/Core/Form/FormStateInterface.php
+++ b/core/lib/Drupal/Core/Form/FormStateInterface.php
@@ -1106,6 +1106,6 @@ public function cleanValues();
    *
    * @return \Drupal\Core\Form\FormStateInterface
    */
-  public function getFormStateForSubform(array $subform);
+  public function getSubFormState(array $subform);
 
 }
diff --git a/core/lib/Drupal/Core/Form/SubFormState.php b/core/lib/Drupal/Core/Form/SubFormState.php
index 746dfc7..9fe3df6 100644
--- a/core/lib/Drupal/Core/Form/SubFormState.php
+++ b/core/lib/Drupal/Core/Form/SubFormState.php
@@ -76,7 +76,7 @@ protected function getSubFormProperty($property) {
    * @return string[]
    *   The parent keys (#array_parents).
    */
-  protected function getSubFormParents() {
+  protected function getArrayParents() {
     return $this->getSubFormProperty('#array_parents');
   }
 
@@ -86,7 +86,7 @@ protected function getSubFormParents() {
    * @return string[]
    *   The parent keys (#parents).
    */
-  protected function getSubFormStateParents() {
+  protected function getParents() {
     return $this->getSubFormProperty('#parents');
   }
 
@@ -95,7 +95,7 @@ protected function getSubFormStateParents() {
    */
   public function &getValues() {
     $exists = NULL;
-    $values = &NestedArray::getValue(parent::getValues(), $this->getSubFormStateParents(), $exists);
+    $values = &NestedArray::getValue(parent::getValues(), $this->getParents(), $exists);
     if (!$exists) {
       $values = [];
     }
@@ -110,7 +110,7 @@ public function &getValues() {
   /**
    * {@inheritdoc}
    */
-  public function getFormStateForSubform(array $element) {
+  public function getSubFormState(array $element) {
     return static::createForSubform($element, $this);
   }
 
diff --git a/core/lib/Drupal/Core/Plugin/PluginFormInterface.php b/core/lib/Drupal/Core/Plugin/PluginFormInterface.php
index 043f405..6c9a98c 100644
--- a/core/lib/Drupal/Core/Plugin/PluginFormInterface.php
+++ b/core/lib/Drupal/Core/Plugin/PluginFormInterface.php
@@ -35,7 +35,7 @@
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form. Calling code should pass on a sub form
    *   state created through
-   *   \Drupal\Core\Form\FormStateInterface::createFormFormElement().
+   *   \Drupal\Core\Form\FormStateInterface::getSubFormState().
    *
    * @return array
    *   The form structure.
@@ -51,7 +51,7 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form. Calling code should pass on a sub form
    *   state created through
-   *   \Drupal\Core\Form\FormStateInterface::createFormFormElement().
+   *   \Drupal\Core\Form\FormStateInterface::getSubFormState().
    */
   public function validateConfigurationForm(array &$form, FormStateInterface $form_state);
 
@@ -64,7 +64,7 @@ public function validateConfigurationForm(array &$form, FormStateInterface $form
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form. Calling code should pass on a sub form
    *   state created through
-   *   \Drupal\Core\Form\FormStateInterface::createFormFormElement().
+   *   \Drupal\Core\Form\FormStateInterface::getSubFormState().
    */
   public function submitConfigurationForm(array &$form, FormStateInterface $form_state);
 
diff --git a/core/modules/block/src/BlockForm.php b/core/modules/block/src/BlockForm.php
index 0c3287f..388d091 100644
--- a/core/modules/block/src/BlockForm.php
+++ b/core/modules/block/src/BlockForm.php
@@ -126,7 +126,7 @@ public function form(array $form, FormStateInterface $form_state) {
 
     $form['#tree'] = TRUE;
     $form['settings'] = [];
-    $subform_state = $form_state->getFormStateForSubform($form['settings']);
+    $subform_state = $form_state->getSubFormState($form['settings']);
     $form['settings'] = $entity->getPlugin()->buildConfigurationForm($form['settings'], $subform_state);
     $form['visibility'] = $this->buildVisibilityInterface([], $form_state);
 
@@ -287,7 +287,7 @@ public function validateForm(array &$form, FormStateInterface $form_state) {
 
     // The Block Entity form puts all block plugin form elements in the
     // settings form element, so just pass that to the block for validation.
-    $this->entity->getPlugin()->validateConfigurationForm($form['settings'], $form_state->getFormStateForSubform($form['settings']));
+    $this->entity->getPlugin()->validateConfigurationForm($form['settings'], $form_state->getSubFormState($form['settings']));
     $this->validateVisibility($form, $form_state);
   }
 
@@ -311,7 +311,7 @@ protected function validateVisibility(array $form, FormStateInterface $form_stat
 
       // Allow the condition to validate the form.
       $condition = $form_state->get(['conditions', $condition_id]);
-      $condition->validateConfigurationForm($form['visibility'][$condition_id], $form_state->getFormStateForSubform($form['visibility'][$condition_id]));
+      $condition->validateConfigurationForm($form['visibility'][$condition_id], $form_state->getSubFormState($form['visibility'][$condition_id]));
     }
   }
 
@@ -324,13 +324,13 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
     $entity = $this->entity;
     // The Block Entity form puts all block plugin form elements in the
     // settings form element, so just pass that to the block for submission.
-    $entity->getPlugin()->submitConfigurationForm($form['settings'], $form_state->getFormStateForSubform($form['settings']));
+    $entity->getPlugin()->submitConfigurationForm($form['settings'], $form_state->getSubFormState($form['settings']));
 
     // Submit visibility condition settings.
     foreach ($form_state->getValue('visibility') as $condition_id => $values) {
       // Allow the condition to submit the form.
       $condition = $form_state->get(['conditions', $condition_id]);
-      $condition->submitConfigurationForm($form['visibility'][$condition_id], $form_state->getFormStateForSubform($form['visibility'][$condition_id]));
+      $condition->submitConfigurationForm($form['visibility'][$condition_id], $form_state->getSubFormState($form['visibility'][$condition_id]));
 
       if ($condition instanceof ContextAwarePluginInterface) {
         $context_mapping = isset($values['context_mapping']) ? $values['context_mapping'] : [];
diff --git a/core/modules/image/src/Form/ImageEffectFormBase.php b/core/modules/image/src/Form/ImageEffectFormBase.php
index d3c0396..def903f 100644
--- a/core/modules/image/src/Form/ImageEffectFormBase.php
+++ b/core/modules/image/src/Form/ImageEffectFormBase.php
@@ -79,7 +79,7 @@ public function buildForm(array $form, FormStateInterface $form_state, ImageStyl
     );
 
     $form['data'] = [];
-    $subform_state = $form_state->getFormStateForSubform($form['data']);
+    $subform_state = $form_state->getSubFormState($form['data']);
     $form['data'] = $this->imageEffect->buildConfigurationForm($form['data'], $subform_state);
     $form['data']['#tree'] = TRUE;
 
@@ -109,7 +109,7 @@ public function buildForm(array $form, FormStateInterface $form_state, ImageStyl
   public function validateForm(array &$form, FormStateInterface $form_state) {
     // The image effect configuration is stored in the 'data' key in the form,
     // pass that through for validation.
-    $this->imageEffect->validateConfigurationForm($form, $form_state->getFormStateForSubform($form['data']));
+    $this->imageEffect->validateConfigurationForm($form['data'], $form_state->getSubFormState($form['data']));
   }
 
   /**
@@ -120,7 +120,7 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
 
     // The image effect configuration is stored in the 'data' key in the form,
     // pass that through for submission.
-    $this->imageEffect->submitConfigurationForm($form, $form_state->getFormStateForSubform($form['data']));
+    $this->imageEffect->submitConfigurationForm($form['data'], $form_state->getSubFormState($form['data']));
 
     $this->imageEffect->setWeight($form_state->getValue('weight'));
     if (!$this->imageEffect->getUuid()) {
diff --git a/core/tests/Drupal/Tests/Core/Form/FormStateTest.php b/core/tests/Drupal/Tests/Core/Form/FormStateTest.php
index fd98431..71d1097 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormStateTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormStateTest.php
@@ -420,9 +420,9 @@ public function testCleanValues($form_state) {
   }
 
   /**
-   * @covers ::getFormStateForSubform
+   * @covers ::getSubFormState
    */
-  public function testGetFormStateForSubform() {
+  public function testGetSubFormState() {
     $form_state = new FormState();
     $element = [
       '#parents' => ['foo'],
@@ -430,7 +430,7 @@ public function testGetFormStateForSubform() {
       'bar' => [],
     ];
 
-    $sub_form_state = $form_state->getFormStateForSubform($element);
+    $sub_form_state = $form_state->getSubFormState($element);
     $this->assertNotSame($form_state, $sub_form_state);
     $this->assertInstanceOf(FormStateInterface::class, $sub_form_state);
   }
diff --git a/core/tests/Drupal/Tests/Core/Form/SubFormStateTest.php b/core/tests/Drupal/Tests/Core/Form/SubFormStateTest.php
index 2836324..d516d9a 100644
--- a/core/tests/Drupal/Tests/Core/Form/SubFormStateTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/SubFormStateTest.php
@@ -51,9 +51,9 @@ class SubFormStateTest extends UnitTestCase {
   ];
 
   /**
-   * @covers ::getFormStateForSubform
+   * @covers ::getSubFormState
    */
-  public function testGetFormStateForSubform() {
+  public function testGetSubFormState() {
     $form_state = new FormState();
     $element = [
       '#parents' => ['foo'],
@@ -61,13 +61,15 @@ public function testGetFormStateForSubform() {
       'bar' => [],
     ];
 
-    $sub_form_state = $form_state->getFormStateForSubform($element);
+    $sub_form_state = $form_state->getSubFormState($element);
     $this->assertNotSame($form_state, $sub_form_state);
     $this->assertInstanceOf(FormStateInterface::class, $sub_form_state);
   }
 
   /**
    * @covers ::getValues
+   * @covers ::getParents
+   * @covers ::getSubFormProperty
    *
    * @dataProvider providerTestGetValues
    *
@@ -79,7 +81,7 @@ public function testGetValues(array $parents, $expected) {
     $form_state->setValues($this->initialValues);
 
     $element = NestedArray::getValue($this->element, $parents);
-    $sub_form_state = $form_state->getFormStateForSubform($element);
+    $sub_form_state = $form_state->getSubFormState($element);
     $sub_values = $sub_form_state->getValues();
     $this->assertSame($expected, $sub_values);
   }
@@ -88,13 +90,19 @@ public function testGetValues(array $parents, $expected) {
    * Provides data to self::testGetValues().
    */
   public function providerTestGetValues() {
-    return [
-      [['dog'], $this->initialValues['dog']],
+    $data = [];
+    $data['exist'] = [
+      ['dog'],
+      $this->initialValues['dog'],
     ];
+
+    return $data;
   }
 
   /**
    * @covers ::getValues
+   * @covers ::getParents
+   * @covers ::getSubFormProperty
    *
    * @dataProvider providerTestGetValuesBroken
    *
@@ -111,10 +119,17 @@ public function testGetValuesBroken(array $parents, $expected) {
    * Provides data to self::testGetValuesBroken().
    */
   public function providerTestGetValuesBroken() {
-    return [
-      [['foo'], $this->initialValues['foo']],
-      [['dog', 'name'], 'Dodger'],
+    $data = [];
+    $data['exist'] = [
+      ['foo'],
+      $this->initialValues['foo'],
+    ];
+    $data['nested'] = [
+      ['dog', 'name'],
+      'Dodger',
     ];
+
+    return $data;
   }
 
   /**
@@ -127,7 +142,7 @@ public function testGetValue($parents, $key, $expected, $default = NULL) {
     $form_state->setValues($this->initialValues);
 
     $element = NestedArray::getValue($this->element, $parents);
-    $sub_form_state = $form_state->getFormStateForSubform($element);
+    $sub_form_state = $form_state->getSubFormState($element);
     $sub_values = $sub_form_state->getValue($key, $default);
     $this->assertSame($expected, $sub_values);
   }
@@ -136,9 +151,14 @@ public function testGetValue($parents, $key, $expected, $default = NULL) {
    * Provides data to self::testGetValue().
    */
   public function providerTestGetValue() {
-    return [
-      [['dog'], 'name', 'Dodger'],
+    $data = [];
+    $data['exist'] = [
+      ['dog'],
+      'name',
+      'Dodger',
     ];
+
+    return $data;
   }
 
   /**
@@ -156,9 +176,14 @@ public function testGetValueBroken(array $parents, $key, $expected, $default = N
    * Provides data to self::testGetValueBroken().
    */
   public function providerTestGetValueBroken() {
-    return [
-      [['dog', 'name'], NULL, 'Dodger'],
+    $data = [];
+    $data['nested'] = [
+      ['dog', 'name'],
+      NULL,
+      'Dodger',
     ];
+
+    return $data;
   }
 
   /**
@@ -171,7 +196,7 @@ public function testSetValues($parents, $new_values, $expected) {
     $form_state->setValues($this->initialValues);
 
     $element = NestedArray::getValue($this->element, $parents);
-    $sub_form_state = $form_state->getFormStateForSubform($element);
+    $sub_form_state = $form_state->getSubFormState($element);
     $sub_form_state->setValues($new_values);
     $this->assertSame($expected, $form_state->getValues());
   }
@@ -180,12 +205,16 @@ public function testSetValues($parents, $new_values, $expected) {
    * Provides data to self::testSetValues().
    */
   public function providerTestSetValues() {
-    return [
-      [['dog'], [], [
+    $data = [];
+    $data['exist'] = [
+      ['dog'],
+      [],
+      [
         'foo' => 'bar',
         'dog' => [],
-      ]],
+      ],
     ];
+    return $data;
   }
 
   /**