man mpv
mpv [options] [file|URL|PLAYLIST|-]
...
--playlist=<filename>
Play files according to a playlist file (Supports some common formats.
If no format is detected, it will be treated as list
of files, separated by newline characters. Note that XML playlist
formats are not supported.)
You can play playlists directly and without this option,
however, this option disables any security mechanisms that might be
in place. You may also need this option to load plaintext files as playlist.