Kernel inclusion policy, meta desicion making structure?

[Tim Post <tim.post@netkinetics.net>]

Good day/evening to all.

I was wondering if a meta version of the decision making process that
would be employed to determine if a new contribution does or does not go
into the main stream Linux kernel.

The following abstract demonstrates my question if it does not make
sense:

"There are many file systems made for the Linux kernel. Only some of
them are present by default in released Kernels."

"There is an AoE block module in the Kernel, but not the userspace blade
module. Only one was included."

Does some document exist that shows the decision making process so that
I can easily answer the ultimate question of "Why not" for myself? It
would be fun to examine code until I could answer the question myself,
and very educational for me as a programmer. Once I figure it out, I
"own" just a little more knowledge without pestering you guys.

I would like to write my own lightweight cluster file system and make
modifications to existing cluster file systems. I think first I should
better learn in practice whats wrong with existing before I go improving
it :) This document would be the best starting point for me.

Thank you in advance for any links. My question is obscure and thus hard
to search for in the archives, I post only after doing so.

Best regards,
--Tim