Documentation: i2c: describe devicetree method for instantiating devices

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/Documentation/i2c/instantiating-devices b/Documentation/i2c/instantiating-devices
index c70e7a7638d1e6e66cbddd3cf7800325560cad28..6df095a6071e44981cd93d17785758d218cb332b 100644 (file)
--- a/Documentation/i2c/instantiating-devices
+++ b/Documentation/i2c/instantiating-devices
@@ -8,8 +8,8 @@ reason, the kernel code must instantiate I2C devices explicitly. There are
 several ways to achieve this, depending on the context and requirements.
 
 
-Method 1: Declare the I2C devices by bus number
------------------------------------------------
+Method 1a: Declare the I2C devices by bus number
+------------------------------------------------
 
 This method is appropriate when the I2C bus is a system bus as is the case
 for many embedded systems. On such systems, each I2C bus has a number
@@ -51,6 +51,36 @@ The devices will be automatically unbound and destroyed when the I2C bus
 they sit on goes away (if ever.)
 
 
+Method 1b: Declare the I2C devices via devicetree
+-------------------------------------------------
+
+This method has the same implications as method 1a. The declaration of I2C
+devices is here done via devicetree as subnodes of the master controller.
+
+Example:
+
+       i2c1: i2c@400a0000 {
+               /* ... master properties skipped ... */
+               clock-frequency = <100000>;
+
+               flash@50 {
+                       compatible = "atmel,24c256";
+                       reg = <0x50>;
+               };
+
+               pca9532: gpio@60 {
+                       compatible = "nxp,pca9532";
+                       gpio-controller;
+                       #gpio-cells = <2>;
+                       reg = <0x60>;
+               };
+       };
+
+Here, two devices are attached to the bus using a speed of 100kHz. For
+additional properties which might be needed to set up the device, please refer
+to its devicetree documentation in Documentation/devicetree/bindings/.
+
+
 Method 2: Instantiate the devices explicitly
 --------------------------------------------