Retargetting GCC for new architectures HOWTO

[S Talha Ergün <ergunst at gmail dot com>]

Hi,

Is there any guide to learn how to target GCC to a custom target for 
current version 9.2?

I've found some resources for 4.9 version but things seem changed. I've 
tried copying other architectures just to be able to build something but 
i can not understand how many files i need to change.

If i follow the GCC Internals manual here:

    https://gcc.gnu.org/onlinedocs/gccint/Back-End.html

I get an error that it can not compute suffixes.

If i follow the guide here :

    https://gcc.gnu.org/simtest-howto.html

I get another error saying :

    configure: error: *** unknown target vector CustomTarget_elf32_be_vec

I am reading the internals for understanding how things work and how a 
custom target can be created. Is there anything i am missing?

Thanks in advance.