only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/migrate/src/Plugin/MigrationProviderInterface.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\migrate\Plugin;
+
+/**
+ * An interface to get the plugin provider.
+ */
+interface MigrationProviderInterface {
+
+  /**
+   * Gets the plugin provider.
+   *
+   * @return string|null
+   *   The plugin provider or NULL if a provider is not found. Note that for a
+   *   source plugin the provider is expected to be the name of the extension in
+   *   the source database.
+   */
+  public function getProvider();
+
+}