coreboot Redundancy / Documentation

[mkopec]

Brief description

We need documentation on how to use the redundancy feature and how to verify it is working. The documentation should cover an overview of the feature, description on how to update, and how to verify that the feature is working as expected.

Where applicable, the update instructions should be updated to reflect the new update flow.

Deliverable

PR to Dasharo/docs

[SergiiDmytruk]

It may be worth describing implementation details in upstream's documentation rather than Dasharo. Nothing extensive, just key points based on the patches:

• names of bootblock and CBFS sections used by the feature
• name of the CMOS option, when its value gets applied to PCH configuration
• where and how main CBFS region is selected
• etc.

This should increase the probability of the feature getting traction in upstream.

[SergiiDmytruk]

All done (merged):

• upstream side: https://review.coreboot.org/c/coreboot/+/90412
• Dasharo side: docs/guides/redundancy.md: add docs#1218 (live at https://docs.dasharo.com/guides/redundancy/)