media: docs: Document colorimetry class

Add a document for ext control colorimetry class.
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/userspace-api/media/v4l/common.rst

@@ -51,6 +51,7 @@ applicable to all devices.
     ext-ctrls-fm-tx
     ext-ctrls-fm-rx
     ext-ctrls-detect
+    ext-ctrls-colorimetry
     fourcc
     format
     planar-apis

Documentation/userspace-api/media/v4l/ext-ctrls-colorimetry.rst

+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _colorimetry-controls:
+
+*****************************
+Colorimetry Control Reference
+*****************************
+
+The Colorimetry class includes controls for High Dynamic Range
+imaging for representing colors in digital images and video. The
+controls should be used for video and image encoding and decoding
+as well as in HDMI receivers and transmitters.
+
+Colorimetry Control IDs
+-----------------------
+
+.. _colorimetry-control-id:
+
+``V4L2_CID_COLORIMETRY_CLASS (class)``
+    The Colorimetry class descriptor. Calling
+    :ref:`VIDIOC_QUERYCTRL` for this control will
+    return a description of this control class.

Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst

@@ -402,6 +402,10 @@ still cause this situation.
       - 0xa40000
       - The class containing stateless codec controls. These controls are
 	described in :ref:`codec-stateless-controls`.
+    * - ``V4L2_CTRL_CLASS_COLORIMETRY``
+      - 0xa50000
+      - The class containing colorimetry controls. These controls are
+	described in :ref:`colorimetry-controls`.
 
 Return Value
 ============