Documentation/gpu: Add basic page for HUBP

Create the HUBP documentation page and add the doc references to extract
the HUBP code documentation.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Harry Wentland <Harry.Wentland@amd.com>
Cc: Hamza Mahfooz <hamza.mahfooz@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Documentation/gpu/amdgpu/display/dcn-blocks.rst

+==========
+DCN Blocks
+==========
+
+In this section, you will find some extra details about some of the DCN blocks
+and the code documentation when it is automatically generated.
+
+HUBP
+----
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/hubp.h
+   :doc: overview
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/hubp.h
+   :export:
+
+.. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/hubp.h
+   :internal:

Documentation/gpu/amdgpu/display/index.rst

@@ -28,5 +28,6 @@ table of content:
    display-manager.rst
    dc-debug.rst
    dcn-overview.rst
+   dcn-blocks.rst
    mpo-overview.rst
    dc-glossary.rst

drivers/gpu/drm/amd/display/dc/inc/hw/hubp.h

@@ -26,13 +26,24 @@
 #ifndef __DAL_HUBP_H__
 #define __DAL_HUBP_H__
 
+/**
+ * DOC: overview
+ *
+ * Display Controller Hub (DCHUB) is the gateway between the Scalable Data Port
+ * (SDP) and DCN. This component has multiple features, such as memory
+ * arbitration, rotation, and cursor manipulation.
+ *
+ * There is one HUBP allocated per pipe, which fetches data and converts
+ * different pixel formats (i.e. ARGB8888, NV12, etc) into linear, interleaved
+ * and fixed-depth streams of pixel data.
+ */
+
 #include "mem_input.h"
 #include "cursor_reg_cache.h"
 
 #define OPP_ID_INVALID 0xf
 #define MAX_TTU 0xffffff
 
-
 enum cursor_pitch {
 	CURSOR_PITCH_64_PIXELS = 0,
 	CURSOR_PITCH_128_PIXELS,