i2c: Document i2c_new_device()

Document the new i2c_new_device(), i2c_new_probed_device() and
i2c_unregister_device() functions.

Signed-off-by: Jean Delvare <[e-mail]>

Documentation/i2c/writing-clients

···
 match, so hotplug/coldplug mechanisms will modprobe the driver.
 
 
+Device Creation (Standard driver model)
+---------------------------------------
+
+If you know for a fact that an I2C device is connected to a given I2C bus,
+you can instantiate that device by simply filling an i2c_board_info
+structure with the device address and driver name, and calling
+i2c_new_device().  This will create the device, then the driver core will
+take care of finding the right driver and will call its probe() method.
+If a driver supports different device types, you can specify the type you
+want using the type field.  You can also specify an IRQ and platform data
+if needed.
+
+Sometimes you know that a device is connected to a given I2C bus, but you
+don't know the exact address it uses.  This happens on TV adapters for
+example, where the same driver supports dozens of slightly different
+models, and I2C device addresses change from one model to the next.  In
+that case, you can use the i2c_new_probed_device() variant, which is
+similar to i2c_new_device(), except that it takes an additional list of
+possible I2C addresses to probe.  A device is created for the first
+responsive address in the list.  If you expect more than one device to be
+present in the address range, simply call i2c_new_probed_device() that
+many times.
+
+The call to i2c_new_device() or i2c_new_probed_device() typically happens
+in the I2C bus driver. You may want to save the returned i2c_client
+reference for later use.
+
+
+Device Deletion (Standard driver model)
+---------------------------------------
+
+Each I2C device which has been created using i2c_new_device() or
+i2c_new_probed_device() can be unregistered by calling
+i2c_unregister_device().  If you don't call it explicitly, it will be
+called automatically before the underlying I2C bus itself is removed, as a
+device can't survive its parent in the device driver model.
+
+
 Legacy Driver Binding Model
 ---------------------------