Based on the Gentoo wiki ---> wpa_supplicant ---> the diff page of gitweb,
the -M option(CONFIG_MATCH_IFACE option) are used to descirbe matching rules
with a wildcard interface name.
But the description doesn't appear in the wpa_supplicant wiki page and relevant
pages clearly, which makes some confuse to those who are not familiar with these
Advice: I think it's maybe better to add the description of -M option to the wpa_
suppliant wiki page(using things like "Tips" or "Comment" at the beginning of the
page),wpa_supplicant manual page and wpa_supplicant.conf manual page.