media: docs: uAPI: dvb/decoder: completing the documentation

The existing documentation of the legacy DVB Decoder API was incomplete.

Revising the documentation, adding missing parts and arranging the
documentation files new.

This patch contains the new index file and links to it.

Link: https://lore.kernel.org/linux-media/20240128233249.32794-2-herdler@nurfuerspam.de
Signed-off-by: Stefan Herdler <herdler@nurfuerspam.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

2 files changed, 62 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/dvb/legacy_dvb_apis.rst b/Documentation/userspace-api/media/dvb/legacy_dvb_apis.rst
index b97d56ee543c..ffe8325749e5 100644
--- a/Documentation/userspace-api/media/dvb/legacy_dvb_apis.rst
+++ b/Documentation/userspace-api/media/dvb/legacy_dvb_apis.rst
@@ -23,3 +23,4 @@ DVB-S2, DVB-T2, ISDB, etc.
     :maxdepth: 1
 
     frontend_legacy_dvbv3_api
+    legacy_dvb_decoder_api
diff --git a/Documentation/userspace-api/media/dvb/legacy_dvb_decoder_api.rst b/Documentation/userspace-api/media/dvb/legacy_dvb_decoder_api.rst
new file mode 100644
index 000000000000..f58985a6e63c
--- /dev/null
+++ b/Documentation/userspace-api/media/dvb/legacy_dvb_decoder_api.rst
@@ -0,0 +1,61 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later OR GPL-2.0
+
+.. _legacy_dvb_decoder_api:
+
+============================
+Legacy DVB MPEG Decoder APIs
+============================
+
+.. _legacy_dvb_decoder_notes:
+
+General Notes
+=============
+
+This API has originally been designed for DVB only and is therefore limited to
+the :ref:`legacy_dvb_decoder_formats` used in such digital TV-broadcastsystems.
+
+To circumvent this limitations the more versatile :ref:`V4L2 <v4l2spec>` API has
+been designed. Which replaces this part of the DVB API.
+
+Nevertheless there have been projects build around this API.
+To ensure compatibility this API is kept as it is.
+
+.. attention:: Do **not** use this API in new drivers!
+
+    For audio and video use the :ref:`V4L2 <v4l2spec>` and ALSA APIs.
+
+    Pipelines should be set up using the :ref:`Media Controller  API<media_controller>`.
+
+Practically the decoders seem to be treated differently. The application typically
+knows which decoder is in use or it is specially written for one decoder type.
+Querying capabilities are rarely used because they are already known.
+
+
+.. _legacy_dvb_decoder_formats:
+
+Data Formats
+============
+
+The API has been designed for DVB and compatible broadcastsystems.
+Because of that fact the only supported data formats are ISO/IEC 13818-1
+compatible MPEG streams. The supported payloads may vary depending on the
+used decoder.
+
+Timestamps are always MPEG PTS as defined in ITU T-REC-H.222.0 /
+ISO/IEC 13818-1, if not otherwise noted.
+
+For storing recordings typically TS streams are used, in lesser extent PES.
+Both variants are commonly accepted for playback, but it may be driver dependent.
+
+
+
+
+Table of Contents
+=================
+
+.. toctree::
+    :maxdepth: 2
+
+    legacy_dvb_video
+    legacy_dvb_audio
+    legacy_dvb_osd