* Analog Devices AD7173 and similar Analog to Digital Converter (ADC)

Required properties:
	- compatible: Must be one of "adi,ad7172-2", "adi,ad7173-8", "adi,7175-2",
	  "adi,7176-2".
	- reg: SPI chip select number for the device
	- interrupts: IRQ line for the ADC
		see: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
	- spi-max-frequency: See Documentation/devicetree/bindings/spi/spi-bus.txt
	- spi-cpha: See Documentation/devicetree/bindings/spi/spi-bus.txt
	- spi-cpol: See Documentation/devicetree/bindings/spi/spi-bus.txt

Optional properties:
	- adi,channels: List of external channels connected to the ADC:
	  Required properties:
		* #address-cells: Must be 2.
		* #size-cells: Must be 0.

	  The child nodes of this node represent the external channels which are
	  connected to the ADC. If the property is no present no external
	  channels will be assumed to be connected.

	  Each child node represents one channel and has the following
	  properties:
		Required properties:
			* reg: Pins the channel is connected to. The first value specifies
			  the positive input pin, the second value the negative input pin.
		Optional properties:
			* adi,bipolar: If set the channel is used in bipolar mode.


Example:
	ad7173 {
		compatible = "adi,ad7173";
		reg = <0>;
		spi-cpol;
		spi-cpha;
		spi-max-frequency = <100000>;

		adi,channels {
			#address-cells = <2>;
			#size-cells = <0>;

			channel@0,1 {
				reg = <0 1>;
				adi,bipolar;
			};

			channel@2,3 {
				reg = <2 3>;
				adi,bipolar;
			};
		};
	};
