Merge branch 'topic/doc' into for-linus

structure. Any of the usual memory allocators will do, but you'll also

need to initialize a few fields in there:

- channels: should be initialized as a list using the

- ``channels``: should be initialized as a list using the

  INIT_LIST_HEAD macro for example

- src_addr_widths:

- ``src_addr_widths``:

  should contain a bitmask of the supported source transfer width

- dst_addr_widths:

- ``dst_addr_widths``:

  should contain a bitmask of the supported destination transfer width

- directions:

- ``directions``:

  should contain a bitmask of the supported slave directions

  (i.e. excluding mem2mem transfers)

- residue_granularity:

  - Granularity of the transfer residue reported to dma_set_residue.

- ``residue_granularity``:

  granularity of the transfer residue reported to dma_set_residue.

  This can be either:

  - Descriptor

    - Your device doesn't support any kind of residue

  - Descriptor:

    your device doesn't support any kind of residue

    reporting. The framework will only know that a particular

    transaction descriptor is done.

      - Segment

        - Your device is able to report which chunks have been transferred

      - Burst

  - Segment:

    your device is able to report which chunks have been transferred

        - Your device is able to report which burst have been transferred

  - Burst:

    your device is able to report which burst have been transferred

  - dev: should hold the pointer to the ``struct device`` associated

- ``dev``: should hold the pointer to the ``struct device`` associated

  to your current driver instance.

Supported transaction types