Where to submit PRs for plugin issue fixes?

Is https://github.com/volumio/volumio-plugins-sources the correct repo to create issues and submit PRs to? Specifically, I have a PR I would like merged in for the “GPIO Control” plugin. I created an issue and submitted the PR there already, but I am not sure if that is the correct place, as I noticed it looks like this repo might be downstream of some other repos maybe?

Also, is there a guide for submitting PRs to other parts of Volumio?

Sorry, I am kind of new to the GitHub ecosystem, but am not new to software development.