* Spreadtrum serial UART

Required properties:
- compatible: must be one of:
  * "sprd,sc9836-uart"
  * "sprd,sc9860-uart", "sprd,sc9836-uart"

- reg: offset and length of the register set for the device
- interrupts: exactly one interrupt specifier
- clocks: phandles to input clocks.

Example:
	uart0: serial@0 {
		compatible = "sprd,sc9860-uart",
			     "sprd,sc9836-uart";
		reg = <0x0 0x100>;
		interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&ext_26m>;
	};