docs: end user documentation regarding firmware management

[rapphil]

How would you describe the priority of this documentation request

High

Describe the future/missing documentation

infra-controller is able to upgrade firmware for the machines that it manages: BIOS, BMC firmware, etc.

However, this feature is not very well documented and is indirectly mentioned in the documentation.

I would like a proper operator documentation for this feature:

• How infra-controller manages firmware updates.
• What are common cases.
• How to manually trigger a firmware update.
• How to use a newer version of a firmware.

Why it is important?

Likely at some point operators hit bugs that can only be solved by upgrading the firmware. As such I would like a clear guide about how to the latest and greatest firmware artifacts from a vendor.

Code of Conduct

• I agree to follow NCX Infra Controller's Code of Conduct
• I have searched the open documentation issues and have found no duplicates for this documentation issue