How to create your own firmware for Android phones from under Linux?

Question

linux

Hello, many phones, having enough power to implement certain tasks, are abandoned!
But for some communities, custom firmware gives a second life.
Yes, of course it's convenient, but not all phones are custom-made, and sometimes the community leaves altogether ...
In such "Extreme" cases, "Lucky" is for those who can make customizations with a higher version of Android.
For example: I need to install Android-5.0 on an old Samsung-GT-S7390.
Please answer in detail, and most importantly informative - there are no detailed guides on Runet!

Answer 1

there are no detailed guides on runet

Absolutely not? At all? But what is this? Googling for you again? So you never learn anything.
Link to the 4pda forum section, Development of kernels and firmware for Android .