pub fn split(
        self,
    ) -> (
        &'static mut [DmaDescriptor],
        &'static mut [DmaDescriptor],
        &'static mut [u8],
    ) {
        (
            self.rx_descriptors.into_inner(),
            self.tx_descriptors.into_inner(),
            self.buffer,
        )
    }
Consume the buf, returning the rx descriptors, tx descriptors and
buffer.
esp-hal/src/dma/buffers.rs