dt-bindings: i2c: add support for 'i2c-arb' subnode

This gets rid of the need for a pointless 'reg' property for i2c
arbitrators.

I.e. this new and more compact style

	some-arbitrator {
		i2c-arb {
			#address-cells = <1>;
			#size-cells = <0>;

			some-i2c-device@50 {
				reg = <0x50>;
			};
		};
	};

instead of the old

	some-arbitrator {
		#address-cells = <1>;
		#size-cells = <0>;

		i2c@0 {
			reg = <0>;

			#address-cells = <1>;
			#size-cells = <0>;

			some-i2c-device@50 {
				reg = <0x50>;
			};
		};
	};

Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>

2 files changed, 37 insertions, 6 deletions

diff --git a/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt
index 71191ff0e781..248a155414c2 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt
@@ -44,8 +44,7 @@ Required properties:
 - our-claim-gpio: The GPIO that we use to claim the bus.
 - their-claim-gpios: The GPIOs that the other sides use to claim the bus.
   Note that some implementations may only support a single other master.
-- Standard I2C mux properties. See i2c-mux.txt in this directory.
-- Single I2C child bus node at reg 0. See i2c-mux.txt in this directory.
+- I2C arbitration bus node. See i2c-arb.txt in this directory.
 
 Optional properties:
 - slew-delay-us: microseconds to wait for a GPIO to go high. Default is 10 us.
@@ -63,8 +62,6 @@ Example:
 
         i2c-arbitrator {
                 compatible = "i2c-arb-gpio-challenge";
-                #address-cells = <1>;
-                #size-cells = <0>;
 
                 i2c-parent = <&{/i2c@12CA0000}>;
 
@@ -74,8 +71,7 @@ Example:
                 wait-retry-us = <3000>;
                 wait-free-us = <50000>;
 
-                i2c@0 {
-                        reg = <0>;
+                i2c-arb {
                         #address-cells = <1>;
                         #size-cells = <0>;
 
diff --git a/Documentation/devicetree/bindings/i2c/i2c-arb.txt b/Documentation/devicetree/bindings/i2c/i2c-arb.txt
new file mode 100644
index 000000000000..59abf9277bdc
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-arb.txt
@@ -0,0 +1,35 @@
+Common i2c arbitration bus properties.
+
+- i2c-arb child node
+
+Required properties for the i2c-arb child node:
+- #address-cells = <1>;
+- #size-cells = <0>;
+
+Optional properties for i2c-arb child node:
+- Child nodes conforming to i2c bus binding
+
+
+Example :
+
+        /*
+           An NXP pca9541 I2C bus master selector at address 0x74
+           with a NXP pca8574 GPIO expander attached.
+         */
+
+        arb@74 {
+                compatible = "nxp,pca9541";
+                reg = <0x74>;
+
+                i2c-arb {
+                        #address-cells = <1>;
+                        #size-cells = <0>;
+
+                        gpio@38 {
+                                compatible = "nxp,pca8574";
+                                reg = <0x38>;
+                                #gpio-cells = <2>;
+                                gpio-controller;
+                        };
+                };
+        };