media: uapi: h264: clarify expected scaling_list_4x4/8x8 order

Clarify that the expected order of scaling lists should follow the order
they are listed in the H264 standard.

The expected scaling list order,
for 4x4: Intra Y, Intra Cb, Intra Cr, Inter Y, Inter Cb, Inter Cr,
for 8x8: Intra Y, Inter Y, Intra Cb, Inter Cb, Intra Cr, Inter Cr.

Also clarify that the values in a scaling list should be in matrix order,
the same value order that vaapi, vdpau and nvdec use.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/media/uapi/v4l/ext-ctrls-codec.rst

@@ -1713,10 +1713,14 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
 
     * - __u8
       - ``scaling_list_4x4[6][16]``
-      -
+      - Scaling matrix after applying the inverse scanning process.
+        Expected list order is Intra Y, Intra Cb, Intra Cr, Inter Y,
+        Inter Cb, Inter Cr.
     * - __u8
       - ``scaling_list_8x8[6][64]``
-      -
+      - Scaling matrix after applying the inverse scanning process.
+        Expected list order is Intra Y, Inter Y, Intra Cb, Inter Cb,
+        Intra Cr, Inter Cr.
 
 ``V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS (struct)``
     Specifies the slice parameters (as extracted from the bitstream)