I definitely borrowed inspiration from @torek's answer. But here, I put it into action:

• Start submodule

  git submodule add https://github.com/dipy/dipy.git

• At this point, you will see the .gitmodule file:

  [submodule "dipy"]
    path = dipy
    url = https://github.com/dipy/dipy.git
  

• Adjust submodule hash:

  cd dipy

  git checkout 1.1.1

  #confirm that you got the desired git tag

  git log -1

• Add the tag to main repository's git tree:

  cd ../

  git add dipy

  git commit -m 'add dipy==1.1.1 to submodule'

• Next time clone your repository and you will get the desired tag in submodule:

  git clone --recurse-submodules [email protected]:pnlbwh/dMRIharmonization.git

  cd dMRIharmonization/dipy

  #confirm that you got the desired submodule tag

  git log -1