Documentation: i2c: mention ACPI method for instantiating devices

Signed-off-by: NWolfram Sang <wsa@the-dreams.de>
Acked-by: NGuenter Roeck <linux@roeck-us.net>

Documentation/i2c/instantiating-devices

@@ -81,6 +81,13 @@ additional properties which might be needed to set up the device, please refer
 to its devicetree documentation in Documentation/devicetree/bindings/.
 
 
+Method 1c: Declare the I2C devices via ACPI
+-------------------------------------------
+
+ACPI can also describe I2C devices. There is special documentation for this
+which is currently located at Documentation/acpi/enumeration.txt.
+
+
 Method 2: Instantiate the devices explicitly
 --------------------------------------------