[coreboot] Req: FOSS-restricting firmware hints

[Nico Rikken]

Dear ARM-netbook and Coreboot readers,

In FSFE context we're looking for examples regarding firmware
restrictions on modern computer hardware. This so that we can shed light
on the difficult situation you are all too familiar with. Examples are:

- Trusted Platform Module (TPM) chips
- Secure Boot
- Intel
  - Management Engine
  - Advanced Management Technology
  - Boot Guard

It will be great if you can add some from the top of your head, ideally
including some references. I'll be doing my own research as well, but
your hints will greatly help this process.

Kind regards,
Nico Rikken