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.
+ Consequently, the client must consider invalid the pointer to that
+ descriptor.
+
5. Issue pending DMA requests and wait for callback notification
The transactions in the pending queue can be activated by calling the