I have not contributed to GCC before, so I am not sure how to go about it.
So, I am letting you know what I want to do, so that I can get advice on
the best way to do it.  I have read https://gcc.gnu.org/contribute.html,
and I have
 
Jim Lowden and I have been developing a COBOL front end for GCC.  He's
primarily been parsing the language.  It's been my task to generate the
GENERIC/GIMPLE trees for the parsed code.  We've been working at this for
a couple of years.  We have reached the point where we want to start
submitting patches for the community to evaluate.
 
I figured I would start small, where "small" means mainly one new source
code file of 1,580 lines.