1* Atmel Universal Synchronous Asynchronous Receiver/Transmitter (USART)
2
3Required properties:
4- compatible: Should be "atmel,<chip>-usart" or "atmel,<chip>-dbgu"
5  The compatible <chip> indicated will be the first SoC to support an
6  additional mode or an USART new feature.
7  For the dbgu UART, use "atmel,<chip>-dbgu", "atmel,<chip>-usart"
8- reg: Should contain registers location and length
9- interrupts: Should contain interrupt
10- clock-names: tuple listing input clock names.
11	Required elements: "usart"
12- clocks: phandles to input clocks.
13
14Optional properties:
15- atmel,use-dma-rx: use of PDC or DMA for receiving data
16- atmel,use-dma-tx: use of PDC or DMA for transmitting data
17- {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD line respectively.
18  It will use specified PIO instead of the peripheral function pin for the USART feature.
19  If unsure, don't specify this property.
20- add dma bindings for dma transfer:
21	- dmas: DMA specifier, consisting of a phandle to DMA controller node,
22		memory peripheral interface and USART DMA channel ID, FIFO configuration.
23		Refer to dma.txt and atmel-dma.txt for details.
24	- dma-names: "rx" for RX channel, "tx" for TX channel.
25
26<chip> compatible description:
27- at91rm9200:  legacy USART support
28- at91sam9260: generic USART implementation for SAM9 SoCs
29
30Example:
31- use PDC:
32	usart0: serial@fff8c000 {
33		compatible = "atmel,at91sam9260-usart";
34		reg = <0xfff8c000 0x4000>;
35		interrupts = <7>;
36		clocks = <&usart0_clk>;
37		clock-names = "usart";
38		atmel,use-dma-rx;
39		atmel,use-dma-tx;
40		rts-gpios = <&pioD 15 GPIO_ACTIVE_LOW>;
41		cts-gpios = <&pioD 16 GPIO_ACTIVE_LOW>;
42		dtr-gpios = <&pioD 17 GPIO_ACTIVE_LOW>;
43		dsr-gpios = <&pioD 18 GPIO_ACTIVE_LOW>;
44		dcd-gpios = <&pioD 20 GPIO_ACTIVE_LOW>;
45		rng-gpios = <&pioD 19 GPIO_ACTIVE_LOW>;
46	};
47
48- use DMA:
49	usart0: serial@f001c000 {
50		compatible = "atmel,at91sam9260-usart";
51		reg = <0xf001c000 0x100>;
52		interrupts = <12 4 5>;
53		clocks = <&usart0_clk>;
54		clock-names = "usart";
55		atmel,use-dma-rx;
56		atmel,use-dma-tx;
57		dmas = <&dma0 2 0x3>,
58		       <&dma0 2 0x204>;
59		dma-names = "tx", "rx";
60	};
61