If you face some challenges or you have some question after reading the above Oracle Documentation let me know.
The link you sent just points to the list of starting points. But if you actually go to the section where they list the steps - https://docs.oracle.com/en/middleware/fusion-middleware/220.127.116.11/wccup/upgrading-oracle-webcenter-previous-12c-release.h… - there is no link for starting the upgrade from WebCenter Portal 18.104.22.168.
Have you read the previous chapters of the guide? You will find the steps necessary to upgrade Oracle WebCenter Portal as your starting point is 22.214.171.124 you do not need special steps.
The link you have provided in the past versions it included the 11g to 12c extra steps of WebCenter Portal, but now is moved to another section of the guide.
If you perform sections 3 and 4 is more than enough for Oracle WebCenter Portal.
If your Portal uses Oracle WebCenter Content then you need to consider the rest of sections related to it.
Thanks for the update. Have you performed this upgrade in the past from 126.96.36.199 to 188.8.131.52? Did you execute steps in only section 3 and 4?
Yes, because I had Oracle WebCenter Content and other parts which I needed to upgrade.