How to report kernel panic in 4.4.x

Hallo,

4.4.147 is the last kernel of the 4.4.x series that boots for me. All subsequent versions panic on boot. How do I report this bug? If I'm supposed to use https://bugzilla.kernel.org/ I don't know what to fill into the fields. I don't even know if the longterm kernel falls under "Mainline" or some other tree.

MSB