First, I'd like to see some input from other vendors - is this useful?

I have no objections to it and it comes with an in-kernel driver, so I'm
inclined to accept it, but maybe we should have other modes, etc.?

+ * @NL80211_ATTR_BEACON_TX_MODE: used to configure the beacon tx mode as
+ *      staggered mode = 1 or burst mode = 2 in %NL80211_CMD_START_AP or
+ *      %NL80211_CMD_JOIN_MESH from user-space.

This should refer to the enum, not the hard-coded constants.

+/**
+ * enum nl80211_beacon_tx_mode - Beacon Tx Mode enum.
+ *      Used to configure beacon staggered mode or beacon burst mode.
+ */
+enum nl80211_beacon_tx_mode {

That's missing kernel-doc, and you also don't specify what default
means. Why is it even here?

+	[NL80211_ATTR_BEACON_TX_MODE] = NLA_POLICY_RANGE(NLA_U32, 1,

2),

That really also needs to use the enum, not hard-coded constants...

johannes