Lindent (from kernel source), reformat C code to the Linux kernel (and osmocom) coding standards
cflow to generate flow-graphs from source code
git format-patch -1, generate a patch
checkpatch.pl, check patches for common errors (Ignore x-signed-off-by)
make distcheck catches quite a few errors, run it before sending patches.
git send-email -1 Send a patch to the mailing list (after configuration)
make check: run it and don't introduce regressions