diff --git a/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php b/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php
index bf987e6..b2758de 100644
--- a/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php
+++ b/core/modules/node/lib/Drupal/node/Plugin/Search/NodeSearch.php
@@ -16,6 +16,7 @@
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\KeyValueStore\KeyValueStoreInterface;
 use Drupal\Core\Language\Language;
+use Drupal\Core\Plugin\PluginFormInterface;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\TypedData\AccessibleInterface;
 use Drupal\Core\Database\Query\Condition;
@@ -34,7 +35,7 @@
  *   path = "node"
  * )
  */
-class NodeSearch extends SearchPluginBase implements AccessibleInterface, SearchIndexingInterface {
+class NodeSearch extends SearchPluginBase implements AccessibleInterface, SearchIndexingInterface, PluginFormInterface {
 
   /**
    * A database connection object.
@@ -516,7 +517,7 @@ public function searchFormSubmit(array &$form, array &$form_state) {
   /**
    * {@inheritdoc}
    */
-  public function addToAdminForm(array &$form, array &$form_state) {
+  public function buildConfigurationForm(array $form, array &$form_state) {
     // Output form for defining rank factor weights.
     $form['content_ranking'] = array(
       '#type' => 'details',
@@ -537,12 +538,19 @@ public function addToAdminForm(array &$form, array &$form_state) {
         '#default_value' => variable_get('node_rank_' . $var, 0),
       );
     }
+    return $form;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function submitAdminForm(array &$form, array &$form_state) {
+  public function validateConfigurationForm(array &$form, array &$form_state) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitConfigurationForm(array &$form, array &$form_state) {
     foreach ($this->moduleHandler->invokeAll('ranking') as $var => $values) {
       if (isset($form_state['values']['node_rank_' . $var])) {
         // @todo Fix when https://drupal.org/node/1831632 is in.
diff --git a/core/modules/search/lib/Drupal/search/Form/SearchSettingsForm.php b/core/modules/search/lib/Drupal/search/Form/SearchSettingsForm.php
index d07e346..45f1e09 100644
--- a/core/modules/search/lib/Drupal/search/Form/SearchSettingsForm.php
+++ b/core/modules/search/lib/Drupal/search/Form/SearchSettingsForm.php
@@ -11,6 +11,7 @@
 use Drupal\Core\Extension\ModuleHandler;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\KeyValueStore\KeyValueStoreInterface;
+use Drupal\Core\Plugin\PluginFormInterface;
 use Drupal\search\SearchPluginManager;
 use Drupal\system\SystemConfigFormBase;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -196,7 +197,9 @@ public function buildForm(array $form, array &$form_state) {
 
     // Per plugin settings.
     foreach ($active_plugins as $plugin) {
-      $plugin->addToAdminForm($form, $form_state);
+      if ($plugin instanceof PluginFormInterface) {
+        $form = $plugin->buildConfigurationForm($form, $form_state);
+      }
     }
     // Set #submit so we are sure it's invoked even if one of
     // the active search plugins added its own #submit.
@@ -219,6 +222,12 @@ public function validateForm(array &$form, array &$form_state) {
         form_set_error('default_plugin', t('Your default search plugin is not selected as an active plugin.'));
       }
     }
+    // Handle per-plugin validation logic.
+    foreach ($this->searchPluginManager->getActivePlugins() as $plugin) {
+      if ($plugin instanceof PluginFormInterface) {
+        $plugin->validateConfigurationForm($form, $form_state);
+      }
+    }
   }
 
   /**
@@ -239,7 +248,9 @@ public function submitForm(array &$form, array &$form_state) {
 
     // Handle per-plugin submission logic.
     foreach ($this->searchPluginManager->getActivePlugins() as $plugin) {
-      $plugin->submitAdminForm($form, $form_state);
+      if ($plugin instanceof PluginFormInterface) {
+        $plugin->submitConfigurationForm($form, $form_state);
+      }
     }
 
     // Check whether we are resetting the values.
diff --git a/core/modules/search/lib/Drupal/search/Plugin/SearchInterface.php b/core/modules/search/lib/Drupal/search/Plugin/SearchInterface.php
index b1429b0..21478fe 100644
--- a/core/modules/search/lib/Drupal/search/Plugin/SearchInterface.php
+++ b/core/modules/search/lib/Drupal/search/Plugin/SearchInterface.php
@@ -98,32 +98,4 @@ public function buildResults();
    */
   public function searchFormAlter(array &$form, array &$form_state);
 
-  /**
-   * Adds elements to the search settings form.
-   *
-   * The core search module only invokes this method on active module plugins.
-   *
-   * @param array $form
-   *   Nested array of form elements that comprise the form.
-   * @param array $form_state
-   *   A keyed array containing the current state of the form. The arguments
-   *   that drupal_get_form() was originally called with are available in the
-   *   array $form_state['build_info']['args'].
-   */
-  public function addToAdminForm(array &$form, array &$form_state);
-
-  /**
-   * Handles any submission for elements on the search settings form.
-   *
-   * The core search module only invokes this method on active module plugins.
-   *
-   * @param array $form
-   *   Nested array of form elements that comprise the form.
-   * @param array $form_state
-   *   A keyed array containing the current state of the form. The arguments
-   *   that drupal_get_form() was originally called with are available in the
-   *   array $form_state['build_info']['args'].
-   */
-  public function submitAdminForm(array &$form, array &$form_state);
-
 }
diff --git a/core/modules/search/lib/Drupal/search/Plugin/SearchPluginBase.php b/core/modules/search/lib/Drupal/search/Plugin/SearchPluginBase.php
index 3b2b162..120d8bd 100644
--- a/core/modules/search/lib/Drupal/search/Plugin/SearchPluginBase.php
+++ b/core/modules/search/lib/Drupal/search/Plugin/SearchPluginBase.php
@@ -94,18 +94,4 @@ public function searchFormAlter(array &$form, array &$form_state) {
     // Empty default implementation.
   }
 
- /**
-   * {@inheritdoc}
-   */
-  public function addToAdminForm(array &$form, array &$form_state) {
-    // Empty default implementation.
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function submitAdminForm(array &$form, array &$form_state) {
-    // Empty default implementation.
-  }
-
 }
diff --git a/core/modules/search/tests/modules/search_extra_type/lib/Drupal/search_extra_type/Plugin/Search/SearchExtraTypeSearch.php b/core/modules/search/tests/modules/search_extra_type/lib/Drupal/search_extra_type/Plugin/Search/SearchExtraTypeSearch.php
index 9b40e45..2ea35eb 100644
--- a/core/modules/search/tests/modules/search_extra_type/lib/Drupal/search_extra_type/Plugin/Search/SearchExtraTypeSearch.php
+++ b/core/modules/search/tests/modules/search_extra_type/lib/Drupal/search_extra_type/Plugin/Search/SearchExtraTypeSearch.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Annotation\Translation;
 use Drupal\Core\Config\Config;
+use Drupal\Core\Plugin\PluginFormInterface;
 use Drupal\search\Plugin\SearchPluginBase;
 use Drupal\search\Annotation\SearchPlugin;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -22,7 +23,7 @@
  *   path = "dummy_path"
  * )
  */
-class SearchExtraTypeSearch extends SearchPluginBase {
+class SearchExtraTypeSearch extends SearchPluginBase implements PluginFormInterface {
 
   /**
    * @var \Drupal\Core\Config\Config
@@ -124,7 +125,7 @@ public function buildResults() {
   /**
    * {@inheritdoc}
    */
-  public function addToAdminForm(array &$form, array &$form_state) {
+  public function buildConfigurationForm(array $form, array &$form_state) {
     // Output form for defining rank factor weights.
     $form['extra_type_settings'] = array(
       '#type' => 'fieldset',
@@ -141,12 +142,19 @@ public function addToAdminForm(array &$form, array &$form_state) {
       ),
       '#default_value' => $this->configSettings->get('boost'),
     );
+    return $form;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function submitAdminForm(array &$form, array &$form_state) {
+  public function validateConfigurationForm(array &$form, array &$form_state) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitConfigurationForm(array &$form, array &$form_state) {
     $this->configSettings
       ->set('boost', $form_state['values']['extra_type_settings']['boost'])
       ->save();