media: docs: dev-decoder: add restrictions about CAPTURE buffers

     buffers are out-of-order compared to the ``OUTPUT`` buffers): ``CAPTURE``

     timestamps will not retain the order of ``OUTPUT`` timestamps.

.. note::

   The backing memory of ``CAPTURE`` buffers that are used as reference frames

   by the stream may be read by the hardware even after they are dequeued.

   Consequently, the client should avoid writing into this memory while the

   ``CAPTURE`` queue is streaming. Failure to observe this may result in

   corruption of decoded frames.

   Similarly, when using a memory type other than ``V4L2_MEMORY_MMAP``, the

   client should make sure that each ``CAPTURE`` buffer is always queued with

   the same backing memory for as long as the ``CAPTURE`` queue is streaming.

   The reason for this is that V4L2 buffer indices can be used by drivers to

   identify frames. Thus, if the backing memory of a reference frame is

   submitted under a different buffer ID, the driver may misidentify it and

   decode a new frame into it while it is still in use, resulting in corruption

   of the following frames.

During the decoding, the decoder may initiate one of the special sequences, as

listed below. The sequences will result in the decoder returning all the

``CAPTURE`` buffers that originated from all the ``OUTPUT`` buffers processed