i2c: aspeed: added documentation for Aspeed I2C driver

Added device tree binding documentation for Aspeed I2C busses.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
new file mode 100644 (file)
index 0000000..bd6480b
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
@@ -0,0 +1,48 @@
+Device tree configuration for the I2C busses on the AST24XX and AST25XX SoCs.
+
+Required Properties:
+- #address-cells       : should be 1
+- #size-cells          : should be 0
+- reg                  : address offset and range of bus
+- compatible           : should be "aspeed,ast2400-i2c-bus"
+                         or "aspeed,ast2500-i2c-bus"
+- clocks               : root clock of bus, should reference the APB
+                         clock
+- interrupts           : interrupt number
+- interrupt-parent     : interrupt controller for bus, should reference a
+                         aspeed,ast2400-i2c-ic or aspeed,ast2500-i2c-ic
+                         interrupt controller
+
+Optional Properties:
+- bus-frequency        : frequency of the bus clock in Hz defaults to 100 kHz when not
+                 specified
+- multi-master : states that there is another master active on this bus.
+
+Example:
+
+i2c {
+       compatible = "simple-bus";
+       #address-cells = <1>;
+       #size-cells = <1>;
+       ranges = <0 0x1e78a000 0x1000>;
+
+       i2c_ic: interrupt-controller@0 {
+               #interrupt-cells = <1>;
+               compatible = "aspeed,ast2400-i2c-ic";
+               reg = <0x0 0x40>;
+               interrupts = <12>;
+               interrupt-controller;
+       };
+
+       i2c0: i2c-bus@40 {
+               #address-cells = <1>;
+               #size-cells = <0>;
+               #interrupt-cells = <1>;
+               reg = <0x40 0x40>;
+               compatible = "aspeed,ast2400-i2c-bus";
+               clocks = <&clk_apb>;
+               bus-frequency = <100000>;
+               interrupts = <0>;
+               interrupt-parent = <&i2c_ic>;
+       };
+};