Merge remote-tracking branch 'upstream/3.4' into merge-3.4

modules/features2d/include/opencv2/features2d.hpp

@@ -80,6 +80,10 @@ This section describes approaches based on local 2D features and used to categor
     -   (Python) An example using the features2D framework to perform object categorization can be
         found at opencv_source_code/samples/python/find_obj.py
 
+    @defgroup feature2d_hal Hardware Acceleration Layer
+    @{
+        @defgroup features2d_hal_interface Interface
+    @}
   @}
  */