diff --git a/core/lib/Drupal/Core/Plugin/PluginFormInterface.php b/core/lib/Drupal/Core/Plugin/PluginFormInterface.php
index 9fb3ad5..7c98514 100644
--- a/core/lib/Drupal/Core/Plugin/PluginFormInterface.php
+++ b/core/lib/Drupal/Core/Plugin/PluginFormInterface.php
@@ -33,7 +33,7 @@
    * @param array $form
    *   An associative array containing the structure of the form.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
-   *   The current state of the form.
+   *   The current state of the complete form.
    *
    * @return array
    *   The form structure.
@@ -46,7 +46,11 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
    * @param array $form
    *   An associative array containing the structure of the form.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
-   *   The current state of the form.
+   *   The current state of the complete form. The values submitted for the
+   *   plugin form can be retrieved through
+   *   @code
+   *   \Drupal\Component\Utility\NestedArray::getValue($form_state->getValues(), $form['#parents']);
+   *   @endcode
    */
   public function validateConfigurationForm(array &$form, FormStateInterface $form_state);
 
@@ -56,7 +60,11 @@ public function validateConfigurationForm(array &$form, FormStateInterface $form
    * @param array $form
    *   An associative array containing the structure of the form.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
-   *   The current state of the form.
+   *   The current state of the complete form. The values submitted for the
+   *   plugin form can be retrieved through
+   *   @code
+   *   \Drupal\Component\Utility\NestedArray::getValue($form_state->getValues(), $form['#parents']);
+   *   @endcode
    */
   public function submitConfigurationForm(array &$form, FormStateInterface $form_state);