Usage of files for config

Hello,

I am a beginner of freebsd kernel. I have some doubts regarding the
Makefile generation using files by config. Could you plz answer the
following doubts:

I would like to know the usage of files and files.[arch] in sys/conf.
Basically, I didnt get the advantage of having a common file for
compilation(like files) rather than an individual Makefile in each
subdirectory.

I have read makefile(of mkmakefile.c in config). What is the usage of
"standard", "optional" and "mandatory" and why it is followed by
device.

What are .m files? What are they used for?

Why are some of the rules in the generated makefile *.ln like scsi_all.ln?

What is ${NORMAL_LINT} and ${NORMAL_C} in the generated makefile mean?

Thanks,
Srinivas