va: basetransform: Update documentation.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2495>

docs/plugins/gst_plugins_cache.json

@@ -225831,7 +225831,19 @@
         },
         "filename": "gstva",
         "license": "LGPL",
-        "other-types": {},
+        "other-types": {
+            "GstVaBaseTransform": {
+                "hierarchy": [
+                    "GstVaBaseTransform",
+                    "GstBaseTransform",
+                    "GstElement",
+                    "GstObject",
+                    "GInitiallyUnowned",
+                    "GObject"
+                ],
+                "kind": "object"
+            }
+        },
         "package": "GStreamer Bad Plug-ins",
         "source": "gst-plugins-bad",
         "tracers": {},

sys/va/gstvabasetransform.c

@@ -43,6 +43,13 @@ struct _GstVaBaseTransformPrivate
   GstBufferPool *sinkpad_pool;
 };
 
+/**
+ * GstVaBaseTransform:
+ *
+ * A base class implementation for VA-API filters.
+ *
+ * Since: 1.20
+ */
 #define gst_va_base_transform_parent_class parent_class
 G_DEFINE_TYPE_WITH_CODE (GstVaBaseTransform, gst_va_base_transform,
     GST_TYPE_BASE_TRANSFORM, G_ADD_PRIVATE (GstVaBaseTransform)
@@ -583,6 +590,8 @@ gst_va_base_transform_class_init (GstVaBaseTransformClass * klass)
       GST_DEBUG_FUNCPTR (gst_va_base_transform_set_context);
   element_class->change_state =
       GST_DEBUG_FUNCPTR (gst_va_base_transform_change_state);
+
+  gst_type_mark_as_plugin_api (GST_TYPE_VA_BASE_TRANSFORM, 0);
 }
 
 GstAllocator *