only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Field/FormatterInterface.php
+++ b/core/lib/Drupal/Core/Field/FormatterInterface.php
@@ -82,5 +82,18 @@ public function view(FieldItemListInterface $items);
    *   consecutive numeric indexes starting from 0.
    */
   public function viewElements(FieldItemListInterface $items);
+  
+  /**
+   * Returns the value of a third-party setting, or its default value if absent.
+   *
+   * @param string $module
+   *   The module providing the third-party setting.
+   * @param string $key
+   *   The setting name.
+   *
+   * @return mixed
+   *   The setting value.
+   */
+  public function getThirdPartySetting($module, $key);
 
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Field/PluginSettingsInterface.php
+++ b/core/lib/Drupal/Core/Field/PluginSettingsInterface.php
@@ -64,4 +64,55 @@ public function setSettings(array $settings);
    */
   public function setSetting($key, $value);
 
+  /**
+   * Returns the array of third-party settings.
+   *
+   * The array is keyed by the third-party module which provides the settings,
+   * and includes defaults for missing settings.
+   *
+   * @return mixed
+   *   The array of settings.
+   */
+  public function getThirdPartySettings();
+
+  /**
+   * Returns the value of a third-party setting, or its default value if absent.
+   *
+   * @param string $module
+   *   The module providing the third-party setting.
+   * @param string $key
+   *   The setting name.
+   *
+   * @return mixed
+   *   The setting value.
+   */
+  public function getThirdPartySetting($module, $key);
+
+  /**
+   * Sets the value of a third-party setting for the plugin.
+   *
+   * @param string $module
+   *   The module providing the third-party setting.
+   * @param string $key
+   *   The setting name.
+   * @param mixed $value
+   *   The setting value.
+   *
+   * @return $this
+   */
+  public function setThirdPartySetting($module, $key, $value);
+
+  /**
+   * Sets the third-party settings for the plugin.
+   *
+   * @param array $settings
+   *   The nested array of settings, keyed by the third party module which
+   *   provides the settings. Individual setting are nested below modules, keyed
+   *   by their setting names. Missing settings will be assigned their default
+   *   values.
+   *
+   * @return $this
+   */
+  public function setThirdPartySettings(array $settings);
+
 }