* Texas Instruments' ADC12130/ADC12132/ADC12138

Required properties:
 - compatible: Should be one of
	* "ti,adc12130"
	* "ti,adc12132"
	* "ti,adc12138"
 - reg: SPI chip select number for the device
 - interrupts: Should contain interrupt for EOC (end of conversion)
 - clocks: phandle to conversion clock input
 - spi-max-frequency: Definision as per
	Documentation/devicetree/bindings/spi/spi-bus.txt
 - vref-p-supply: The regulator supply for positive analog voltage reference

Optional properties:
 - vref-n-supply: The regulator supply for negative analog voltage reference
	(Note that this must not go below GND or exceed vref-p)
	If not specified, this is assumed to be analog ground.
 - ti,acquisition-time: The number of conversion clock periods for the S/H's
	acquisition time.  Should be one of 6, 10, 18, 34.  If not specified,
	default value of 10 is used.
	For high source impedances, this value can be increased to 18 or 34.
	For less ADC accuracy and/or slower CCLK frequencies this value may be
	decreased to 6.  See section 6.0 INPUT SOURCE RESISTANCE in the
	datasheet for details.

Example:
adc@0 {
	compatible = "ti,adc12138";
	reg = <0>;
	interrupts = <28 IRQ_TYPE_EDGE_RISING>;
	interrupt-parent = <&gpio1>;
	clocks = <&cclk>;
	vref-p-supply = <&ldo4_reg>;
	spi-max-frequency = <5000000>;
	ti,acquisition-time = <6>;
};