diff --git a/core/modules/migrate/src/Plugin/migrate/process/SubProcess.php b/core/modules/migrate/src/Plugin/migrate/process/SubProcess.php
index 481196d..cb11fc6 100644
--- a/core/modules/migrate/src/Plugin/migrate/process/SubProcess.php
+++ b/core/modules/migrate/src/Plugin/migrate/process/SubProcess.php
@@ -7,7 +7,7 @@
 use Drupal\migrate\Row;
 
 /**
- * Processes associative array value of a row through its own process pipeline.
+ * Runs an array of arrays through its own process pipeline.
  *
  * The sub_process plugin accepts an array of associative arrays and runs each
  * one through its own process pipeline, producing a newly keyed associative
@@ -15,7 +15,8 @@
  *
  * Available configuration keys:
  *   - process: the plugin(s) that will process each element of the source.
- *   - key: runs the process pipeline for the key to determine its dynamic name.
+ *   - key: runs the process pipeline for the key to determine a new dynamic
+ *     name.
  *
  * Examples:
  *
@@ -63,6 +64,48 @@
  * destination value from a previous migration. The display and description
  * fields will simply be mapped.
  *
+ * In the next example, normally the array returned from sub_process will have
+ * its original keys. If you need to change the key, it is possible for the
+ * returned array to be keyed by one of the transformed values in the sub-array.
+ *
+ * @code
+ * source: Array
+ * (
+ *   [format] => 1
+ *   [name] => Filtered HTML
+ * ...
+ *   [filters] => Array
+ *     (
+ *       [0] => Array
+ *         (
+ *           [module] => filter
+ *           [delta] => 2
+ *           [weight] => 0
+ *         )
+ *       [1] => Array
+ *         (
+ *           [module] => filter
+ *           [delta] => 0
+ *           [weight] => 1
+ *         )
+ *    )
+ * )
+ * ...
+ *
+ * process:
+ *   filters:
+ *     plugin: iterator
+ *     source: filters
+ *     key: "@id"
+ *     process:
+ *       id:
+ *         plugin: static_map
+ *         bypass: true
+ *         map:
+ *           filter:
+ *             ...
+ * @endcode
+ *
  * @see \Drupal\migrate\Plugin\MigrateProcessInterface
  *
  * @MigrateProcessPlugin(