doc: linux-wpan: Fulfill the description of missed 802.15.4 APIs

There are more functions and operations which must be used or implemented
in each IEEE 802.15.4 device driver, but are not mentioned in the Device
drivers API section of Documentation/networking/ieee802154.txt.  Therefore,
I want to fulfill the missed part into the documentation with this patch.

Signed-off-by: Jian-Hong Pan <starnight@g.ncu.edu.tw>
Acked-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: Stefan Schmidt <stefan@osg.samsung.com>

Documentation/networking/ieee802154.txt

@@ -97,6 +97,46 @@ The include/net/mac802154.h defines following functions:
  - void ieee802154_unregister_hw(struct ieee802154_hw *hw):
    freeing registered PHY
 
+ - void ieee802154_rx_irqsafe(struct ieee802154_hw *hw, struct sk_buff *skb,
+                              u8 lqi):
+   telling 802.15.4 module there is a new received frame in the skb with
+   the RF Link Quality Indicator (LQI) from the hardware device
+
+ - void ieee802154_xmit_complete(struct ieee802154_hw *hw, struct sk_buff *skb,
+                                 bool ifs_handling):
+   telling 802.15.4 module the frame in the skb is or going to be
+   transmitted through the hardware device
+
+The device driver must implement the following callbacks in the IEEE 802.15.4
+operations structure at least:
+struct ieee802154_ops {
+	...
+	int	(*start)(struct ieee802154_hw *hw);
+	void	(*stop)(struct ieee802154_hw *hw);
+	...
+	int	(*xmit_async)(struct ieee802154_hw *hw, struct sk_buff *skb);
+	int	(*ed)(struct ieee802154_hw *hw, u8 *level);
+	int	(*set_channel)(struct ieee802154_hw *hw, u8 page, u8 channel);
+	...
+};
+
+ - int start(struct ieee802154_hw *hw):
+   handler that 802.15.4 module calls for the hardware device initialization.
+
+ - void stop(struct ieee802154_hw *hw):
+   handler that 802.15.4 module calls for the hardware device cleanup.
+
+ - int xmit_async(struct ieee802154_hw *hw, struct sk_buff *skb):
+   handler that 802.15.4 module calls for each frame in the skb going to be
+   transmitted through the hardware device.
+
+ - int ed(struct ieee802154_hw *hw, u8 *level):
+   handler that 802.15.4 module calls for Energy Detection from the hardware
+   device.
+
+ - int set_channel(struct ieee802154_hw *hw, u8 page, u8 channel):
+   set radio for listening on specific channel of the hardware device.
+
 Moreover IEEE 802.15.4 device operations structure should be filled.
 
 Fake drivers