The nl80211 interface is the netlink based interface which is used by user space daemons such as wpa_supplicant, hostapd, iw tool to configure the lower WiFi device.
The wpa_supplicant/hostapd register to the lower interface as nl80211_driver interface. once registered, the user space daemons can send configurations commands via netlink socket. A snippet of the nl80211 command is provided below
A snippet from the wpa_supplicant readme is provided below
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