Some of the Internet Archive's library partners are asking us about
language metadata for regional languages that don't have standard
codes.  Is there a standard way of dealing with this situation?

Overall we use MARC codes https://www.loc.gov/marc/languages/ which
were last updated in 2007. LOC also maintains ISO639-2
https://www.loc.gov/standards/iso639-2/php/code_list.php last updated
in 2014.

The languages in question are regional languages which are currently
lumped together in both standards. With the recent rise in interest
and funding for regional languages, it's no surprise that some
catalogers want to split these languages out into separate codes.

Thanks!

-- greg