* Linear Technology Micropower octal 8-Bit and 10-Bit DACs

Required properties:
 - compatible: Must be one of the following:
		"lltc,ltc1660"
		"lltc,ltc1665"
 - reg: SPI chip select number for the device
 - vref-supply: Phandle to the voltage reference supply

Recommended properties:
 - spi-max-frequency: Definition as per
	 Documentation/devicetree/bindings/spi/spi-bus.txt.
	 Max frequency for this chip is 5 MHz.

Example:
dac@0 {
	compatible = "lltc,ltc1660";
	reg = <0>;
	spi-max-frequency = <5000000>;
	vref-supply = <&vref_reg>;
};