Netifd: adding info notification support

My goal is to add a way to notify users via netifd about "info" events
for interfaces instead of only "errors", by adding support for a
function called proto_notify_info().

Currently, I am (ab)using proto_notify_error() in to
indicate what is happening during the sometimes long and error prone
process of establishing a mobile data connection. However, most of
the time the events are not strictly speaking "errors", but due to the
way things currently are (unless I am missing something), they are
displayed like errors. This has been the source of some confusion
among users, for instance: "Why does it say 'Error: Connection attempt
in progress' when it probably should say 'Info: connection attempt in
progress'?" Actually, I can think of a number of events like that
which I could use this feature on, which is why I would like to
implement it.

So, is there support for this already, or is this something I can add
to netifd and the corresponding scripts? Would this be a welcome
change upstream or too niche?