MOXA ART DMA Controller

See dma.txt first

Required properties:

- compatible :	Must be "moxa,moxart-dma"
- reg :		Should contain registers location and length
- interrupts :	Should contain an interrupt-specifier for the sole
		interrupt generated by the device
- #dma-cells :	Should be 1, a single cell holding a line request number

Example:

	dma: dma@90500000 {
		compatible = "moxa,moxart-dma";
		reg = <0x90500080 0x40>;
		interrupts = <24 0>;
		#dma-cells = <1>;
	};


Clients:

DMA clients connected to the MOXA ART DMA controller must use the format
described in the dma.txt file, using a two-cell specifier for each channel:
a phandle plus one integer cells.
The two cells in order are:

1. A phandle pointing to the DMA controller.
2. Peripheral identifier for the hardware handshaking interface.

Example:
Use specific request line passing from dma
For example, MMC request line is 5

	mmc: mmc@98e00000 {
		compatible = "moxa,moxart-mmc";
		reg = <0x98e00000 0x5C>;
		interrupts = <5 0>;
		clocks = <&clk_apb>;
		dmas =  <&dma 5>,
			<&dma 5>;
		dma-names = "tx", "rx";
	};
