media: docs: move uAPI book to userspace-api/media

Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee3862 ("docs: Create a user-space API guide").

As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.

Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/v4l/selections-common.rst b/Documentation/userspace-api/media/v4l/selections-common.rst
new file mode 100644
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+.. Permission is granted to copy, distribute and/or modify this
+.. document under the terms of the GNU Free Documentation License,
+.. Version 1.1 or any later version published by the Free Software
+.. Foundation, with no Invariant Sections, no Front-Cover Texts
+.. and no Back-Cover Texts. A copy of the license is included at
+.. Documentation/userspace-api/media/fdl-appendix.rst.
+..
+.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _v4l2-selections-common:
+
+Common selection definitions
+============================
+
+While the :ref:`V4L2 selection API <selection-api>` and
+:ref:`V4L2 subdev selection APIs <v4l2-subdev-selections>` are very
+similar, there's one fundamental difference between the two. On
+sub-device API, the selection rectangle refers to the media bus format,
+and is bound to a sub-device's pad. On the V4L2 interface the selection
+rectangles refer to the in-memory pixel format.
+
+This section defines the common definitions of the selection interfaces
+on the two APIs.
+
+
+.. toctree::
+    :maxdepth: 1
+
+    v4l2-selection-targets
+    v4l2-selection-flags