kernel developer: fine-grained regression report subscription

*Please replace the words in capital letters below with your own:*

**As a kernel developer, I want to be notified only on the regression reports that affect my patches or my area of interest so I can focus on the important problems for me faster and with less noise**

## Background

The current regression reports are sent to general mailing lists that developers can join. However, there's no way to receive only certain kinds of regressions. If I'm not aware of the mailing lists I won't find any regressions unless someone points me to them, if I join the mailing list I'll receive all reports, which is just as bad, as I'll eventually see them most of them as unnecessary noise.

Instead, if a regression is detected to be caused by one of my patches, I'd like to be automatically subscribed to it. If I'm in charge of a subsystem in the kernel, I'd like to be aware of the regressions affecting it and maybe nothing else.

Start by reviewing the existing regression-report mailing-list flow described in the issue and how regressions are associated with patches or kernel subsystems. Done would mean defining and implementing subscriptions that notify developers about regressions caused by their patches or affecting their areas of interest, without sending unrelated reports.

Written by the indexing model from the issue text.