mac80211: add remain-on-channel docs

Add documentation for the new callbacks that I
forgot in the patch adding the callbacks.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -1753,6 +1753,16 @@ enum ieee80211_ampdu_mlme_action {
  *	(also see nl80211.h @NL80211_ATTR_WIPHY_ANTENNA_TX).
  *
  * @get_antenna: Get current antenna configuration from device (tx_ant, rx_ant).
+ *
+ * @remain_on_channel: Starts an off-channel period on the given channel, must
+ *	call back to ieee80211_ready_on_channel() when on that channel. Note
+ *	that normal channel traffic is not stopped as this is intended for hw
+ *	offload. Frames to transmit on the off-channel channel are transmitted
+ *	normally except for the %IEEE80211_TX_CTL_TX_OFFCHAN flag. When the
+ *	duration (which will always be non-zero) expires, the driver must call
+ *	ieee80211_remain_on_channel_expired(). This callback may sleep.
+ * @cancel_remain_on_channel: Requests that an ongoing off-channel period is
+ *	aborted before it expires. This callback may sleep.
  */
 struct ieee80211_ops {
 	int (*tx)(struct ieee80211_hw *hw, struct sk_buff *skb);