GitHub: How to send one pull request per separate commit?

GitHub's Pull Requests are designed to be per-branch, not per-commit. This is deliberate:

After your pull request is sent, any new commits pushed to your branch will automatically be added to the pull request. This is especially useful if you need to make more changes.

If you want to send ten Pull Requests in GitHub you'll have to do it using ten branches. The only exception would be if you wait for each Pull Request to be merged before submitting the next one.

There's a work-around suggested by Grason Koonce that amounts to:

creating successive branches for each piece, and making pull requests against the previous branch point(rather than the target branch).

Once all reviewed and accepted merge in reverse order 5->4, 4->3, 3->2, 2->1, and only then 1->master/target.

It's not pretty but it is a solution.

https://graysonkoonce.com/stacked-pull-requests-keeping-github-diffs-small/