* Maxim 1027/1029/1031 Analog to Digital Converter (ADC)

Required properties:
  - compatible: Should be "maxim,max1027" or "maxim,max1029" or "maxim,max1031"
  - reg: SPI chip select number for the device
  - interrupts: IRQ line for the ADC
  see: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt

Recommended properties:
- spi-max-frequency: Definition as per
                     Documentation/devicetree/bindings/spi/spi-bus.txt

Example:
adc@0 {
	compatible = "maxim,max1027";
	reg = <0>;
	interrupt-parent = <&gpio5>;
	interrupts = <15 IRQ_TYPE_EDGE_RISING>;
	spi-max-frequency = <1000000>;
};