As stated earlier in Chapter 2, there is a MOS document called Oracle 11gR2 Upgrade Companion [see ID 785351.1], which I personally think is a misleading title. It implies that this is a utility of sorts, but it is only a very long document on everything you would ever want to know about upgrading. It applies to every installation type (see the following list of configurations, this is the same list mentioned in Chapter 2 in the Recommended Patches section) and can be very confusing to new DBAs.
Targeted configurations in the upgrade companion:
Generic
Real Application Clusters and CRS
Data Guard (and/or Streams)
Exadata
Oracle e-business suite
The upgrade companion seems to be a document taking all of the possible things that could go wrong with an upgrade all bundled up in one place. I would recommend downloading the companion, and copying all of the text in a document to which you can then add comments or amend as needed. Take out the information that doesn't apply to...