A front end for a language in GCC has the following parts:
gcc containing source
files for that front end.  See The Front End gcc/doc/install.texi. 
gcc/doc/contrib.texi.  If the details are in that front end's
own manual then there should be a link to that manual's list in
contrib.texi. 
gcc/doc/frontends.texi. 
gcc/doc/standards.texi.  This may be a
link to such information in the front end's own manual. 
-x
langgcc/doc/invoke.texi. 
default_compilers in gcc.c for source file
suffixes for that language. 
gcc/testsuite or
runtime library directories.  FIXME: document somewhere how to write
test suite harnesses. 
gcc
directory.  FIXME: document this further. 
gcc/doc/sourcebuild.texi. 
If the front end is added to the official GCC CVS repository, the following are also necessary:
gcc/gccbug.in, and in gnats.html on the GCC web site, as
well as being added to the GNATS database. 
MAINTAINERS. 
index.html and
frontends.html, with any relevant links on
readings.html.  (Front ends that are not an official part of
GCC may also be listed on frontends.html, with relevant links.) 
index.html, and possibly an announcement on the
gcc-announce@gcc.gnu.org mailing list. 
maintainer-scripts/update_web_docs (see Texinfo Manuals)
and the online manuals should be linked to from
onlinedocs/index.html. 
maintainer-scripts/gcc_release
should be updated to generate appropriate tarballs for this front end. 
The associated maintainer-scripts/snapshot-README and
maintainer-scripts/snapshot-index.html files should be updated
to list the tarballs and diffs for this front end. 
maintainer-scripts/update_version should be
updated accordingly. 
CVSROOT/modules in the GCC CVS repository should be updated.