media: v4l: Add definitions for HEVC stateless decoding

This introduces the required definitions for HEVC decoding support with
stateless VPUs. The controls associated to the HEVC slice format provide
the required meta-data for decoding slices extracted from the bitstream.

They are not exported to the public V4L2 API since reworking this API
will likely be needed for covering various use-cases and new hardware.

Multi-slice decoding is exposed as a valid decoding mode to match current
H.264 support but it is not yet implemented.

The interface comes with the following limitations:
* No custom quantization matrices (scaling lists);
* Support for a single temporal layer only;
* No slice entry point offsets support;
* No conformance window support;
* No VUI parameters support;
* No support for SPS extensions: range, multilayer, 3d, scc, 4 bits;
* No support for PPS extensions: range, multilayer, 3d, scc, 4 bits.

Signed-off-by: Paul Kocialkowski <[email protected]>
[[email protected]: use 1ULL in flags defines in hevc-ctrls.h]
Signed-off-by: Hans Verkuil <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

Documentation/media/uapi/v4l/biblio.rst

@@ -131,6 +131,15 @@ ITU-T Rec. H.264 Specification (04/2017 Edition)
 
 :author:    International Telecommunication Union (http://www.itu.ch)
 
+.. _hevc:
+
+ITU H.265/HEVC
+==============
+
+:title:     ITU-T Rec. H.265 | ISO/IEC 23008-2 "High Efficiency Video Coding"
+
+:author:    International Telecommunication Union (http://www.itu.ch), International Organisation for Standardisation (http://www.iso.ch)
+
 .. _jfif:
 
 JFIF