This repo holds the e1000 driver extracted from FreeBSD.
In a clone of the upstream FreeBSD repo, run:
git filter-repo --subdirectory-filter sys/dev/e1000/ --force
git filter-repo --path-regex 'e1000_osdep.[ch]' --invert-paths
git filter-repo --path-regex 'e1000_*' --path 'LICENSE'