* Microchip MCP3911 Dual channel analog front end (ADC)

Required properties:
 - compatible: Should be "microchip,mcp3911"
 - reg: SPI chip select number for the device

Recommended properties:
 - spi-max-frequency: Definition as per
	 Documentation/devicetree/bindings/spi/spi-bus.txt.
	 Max frequency for this chip is 20MHz.

Optional properties:
 - clocks: Phandle and clock identifier for sampling clock
 - interrupt-parent: Phandle to the parent interrupt controller
 - interrupts: IRQ line for the ADC
 - microchip,device-addr: Device address when multiple MCP3911 chips are present on the
	same SPI bus. Valid values are 0-3. Defaults to 0.
 - vref-supply: Phandle to the external reference voltage supply.

Example:
adc@0 {
	compatible = "microchip,mcp3911";
	reg = <0>;
	interrupt-parent = <&gpio5>;
	interrupts = <15 IRQ_TYPE_EDGE_RISING>;
	spi-max-frequency = <20000000>;
	microchip,device-addr = <0>;
	vref-supply = <&vref_reg>;
	clocks = <&xtal>;
};