How-to update a git submodule

I do not use git submodules too often, so I'll write this recipe here, for future reference.

When we have a git repo with a submodule inside, some steps are needed to update both in sync.
This occurs because, the parent repo and the submodule, are actually two independent repos.

This is the workflow I use to update a submodule:

1. Work inside the submodule:

   $ # edit <some files>

   $ git add <some files>

2. Now we have some changes ready to commit and push them:

   $ git commit -m "Edited <some files>

   $ git push

3. Finally, we tell the parent repo that the submodule has changed:

   $ cd the/parent/repo/path

   $ git add the/submodule/repo/path

   $ git commit -m "Updated the submodule"

   $ git push

Syncing everytime a change is made to the submodule is not advisable, think carefully before doing it.
Sometimes we should NOT do it at all (e.g. there are compatibility breaking changes).

The parent repo could point to a previous (and safe) version of the submodule all the required time.
At least while is being adapted to assimilate the submodule updates.