Added device tree binding documentation for Aspeed I2C controller and
busses.

Signed-off-by: Brendan Higgins <brendanhigg...@google.com>
---
Changes for v2:
  - None
Changes for v3:
  - Removed reference to "bus" device tree param
---
 .../devicetree/bindings/i2c/i2c-aspeed.txt         | 61 ++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-aspeed.txt

diff --git a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt 
b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
new file mode 100644
index 0000000..dd11a97
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
@@ -0,0 +1,61 @@
+Device tree configuration for the I2C controller and busses on the AST24XX
+and AST25XX SoCs.
+
+Controller:
+
+       Required Properties:
+       - #address-cells        : should be 1
+       - #size-cells           : should be 1
+       - #interrupt-cells      : should be 1
+       - compatible            : should be "aspeed,ast2400-i2c-controller"
+                                 or "aspeed,ast2500-i2c-controller"
+       - reg                   : address start and range of controller
+       - ranges                : defines address offset and range for busses
+       - interrupts            : interrupt number
+       - clocks                : root clock of bus, should reference the APB
+                                 clock
+       - clock-ranges          : specifies that child busses can inherit clocks
+       - interrupt-controller  : denotes that the controller receives and fires
+                                 new interrupts for child busses
+
+Bus:
+
+       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"
+       - interrupts            : interrupt number
+
+       Optional Properties:
+       - clock-frequency       : frequency of the bus clock in Hz
+                                 defaults to 100 kHz when not specified
+
+Example:
+
+i2c: i2c@1e78a000 {
+       #address-cells = <1>;
+       #size-cells = <1>;
+       #interrupt-cells = <1>;
+
+       compatible = "aspeed,ast2400-i2c-controller";
+       reg = <0x1e78a000 0x40>;
+       ranges = <0 0x1e78a000 0x1000>;
+       interrupts = <12>;
+       clocks = <&clk_apb>;
+       clock-ranges;
+       interrupt-controller;
+
+       i2c0: i2c-bus@40 {
+               #address-cells = <1>;
+               #size-cells = <0>;
+               reg = <0x40 0x40>;
+               compatible = "aspeed,ast2400-i2c-bus";
+               clock-frequency = <100000>;
+               status = "disabled";
+               interrupts = <0>;
+               interrupt-parent = <&i2c>;
+       };
+};
+
-- 
2.8.0.rc3.226.g39d4020

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