serial: sirf: add DT-binding document to describle detailed properties

we defined some special properties for hardware flow control, document them
for DT-binding.

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/devicetree/bindings/tty/serial/sirf-uart.txt b/Documentation/devicetree/bindings/tty/serial/sirf-uart.txt
new file mode 100644 (file)
index 0000000..a2dfc65
--- /dev/null
+++ b/Documentation/devicetree/bindings/tty/serial/sirf-uart.txt
@@ -0,0 +1,33 @@
+* CSR SiRFprimaII/atlasVI Universal Synchronous Asynchronous Receiver/Transmitter *
+
+Required properties:
+- compatible : Should be "sirf,prima2-uart" or "sirf, prima2-usp-uart"
+- reg : Offset and length of the register set for the device
+- interrupts : Should contain uart interrupt
+- fifosize : Should define hardware rx/tx fifo size
+- clocks : Should contain uart clock number
+
+Optional properties:
+- sirf,uart-has-rtscts: we have hardware flow controller pins in hardware
+- rts-gpios: RTS pin for USP-based UART if sirf,uart-has-rtscts is true
+- cts-gpios: CTS pin for USP-based UART if sirf,uart-has-rtscts is true
+
+Example:
+
+uart0: uart@b0050000 {
+       cell-index = <0>;
+       compatible = "sirf,prima2-uart";
+       reg = <0xb0050000 0x1000>;
+       interrupts = <17>;
+       fifosize = <128>;
+       clocks = <&clks 13>;
+};
+
+On the board-specific dts, we can put rts-gpios and cts-gpios like
+
+usp@b0090000 {
+       compatible = "sirf,prima2-usp-uart";
+       sirf,uart-has-rtscts;
+       rts-gpios = <&gpio 15 0>;
+       cts-gpios = <&gpio 46 0>;
+};