doc:dmaengine: clarify DMA desc. pointer after submission

[Vinod Koul <vkoul@kernel.org>]

On 08-02-19, 16:30, Federico Vaga wrote:
> It clarifies that the DMA description pointer returned by
> `dmaengine_prep_*` function should not be used after submission.
> 
> Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
> ---
>  Documentation/driver-api/dmaengine/client.rst | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst
> index fbbb2831f29f..d728e50105eb 100644
> --- a/Documentation/driver-api/dmaengine/client.rst
> +++ b/Documentation/driver-api/dmaengine/client.rst
> @@ -168,6 +168,13 @@ The details of these operations are:
>     dmaengine_submit() will not start the DMA operation, it merely adds
>     it to the pending queue. For this, see step 5, dma_async_issue_pending.
>  
> +   .. note::
> +
> +      After calling ``dmaengine_submit()`` the submitted transfer descriptor
> +      (``struct dma_async_tx_descriptor``) belongs to the DMA engine.
> +      Consequentially, the client must consider invalid the pointer to that

Consequently

> +      descriptor.
> +

Applied after fixing the typo and added tag as Documentation: dmaengine...

>  5. Issue pending DMA requests and wait for callback notification
>  
>     The transactions in the pending queue can be activated by calling the
> -- 
> 2.15.0