Binding for Cadence UART Controller

Required properties:
- compatible : should be "cdns,uart-r1p8", or "xlnx,xuartps"
- reg: Should contain UART controller registers location and length.
- interrupts: Should contain UART controller interrupts.
- clocks: Must contain phandles to the UART clocks
  See ../clocks/clock-bindings.txt for details.
- clock-names: Tuple to identify input clocks, must contain "uart_clk" and "pclk"
  See ../clocks/clock-bindings.txt for details.


Example:
	uart@e0000000 {
		compatible = "cdns,uart-r1p8";
		clocks = <&clkc 23>, <&clkc 40>;
		clock-names = "uart_clk", "pclk";
		reg = <0xE0000000 0x1000>;
		interrupts = <0 27 4>;
	};