I would like to get people working on the iBasso ports working on Rockbox more generally. Usually for rockbox we try to do two different kinds of commits:
1) device specific, so things like new ports, drivers, hardware optimization, etc
2) not device specific, so things like new features, UI changes, plugins, codecs, audio effects, etc that affect all players
Ideally if you want to make a change to the UI or whatever in rockbox (basically, the /apps folder) it should be applicable to many different devices, or at least all devices were it makes sense. Things in the firmware/target tree are usually just for one or a few devices. So if possible, try submitting fixes to the DX50/90 port separately from anything else, and I can just blindly approve them without having to get people to test them on other devices (Android, etc).
If you want to change something that will impact a lot of devices, that is possible too, but much more testing is required.