find list off all users which device is linked to?

I would like to fetch list of users who the specific device is linked to it. is this provided by API?

There is an internal Java API for that, but no HTTP API.

could you show which part of code? is it ok to send a PR to enable this feature in HTTP API?

It might be useful to have this API, but I'm probably ok with it.

As for locating it in the code, look at how notifications work. That's where we get users by device.