NXP SC18IS602/SCIS603

Required properties:
	- compatible : Should be one of
		"nxp,sc18is602"
		"nxp,sc18is602b"
		"nxp,sc18is603"
	- reg: I2C bus address

Optional properties:
	- clock-frequency : external oscillator clock frequency. If not
	  specified, the SC18IS602 default frequency (7372000) will be used.

The clock-frequency property is relevant and needed only if the chip has an
external oscillator (SC18IS603).

Example:

	sc18is603@28 {
		compatible = "nxp,sc18is603";
		reg = <0x28>;
		clock-frequency = <14744000>;
	}
