Add exisiting local git repo as submodule as a submodule to parent directory repo?

git submodule add ./Segmentation1 Segmentation1
# this is optional
git submodule absorbgitdirs Segmentation1
# add submodule's url
git config -f .gitmodules submodule.Segmentation1.url \
        https://github.com/etc/path.git

ref: https://www.reddit.com/r/git/comments/edn49q/how_to_add_existing_local_git_repo_as_a_submodule/

Verified on 24/7/10.