ARM MPS2 UART

Required properties:
- compatible	: Should be "arm,mps2-uart"
- reg		: Address and length of the register set
- interrupts	: Reference to the UART RX, TX and overrun interrupts

Required clocking property:
- clocks	  : The input clock of the UART


Examples:

uart0: serial@40004000 {
	compatible = "arm,mps2-uart";
	reg = <0x40004000 0x1000>;
	interrupts = <0 1 12>;
	clocks = <&sysclk>;
};