From Steven Chan’s blog, https://blogs.oracle.com/stevenChan/entry/ebs_12_2_5_available:

“Instructions for downloading and applying this release update pack (RUP) for the EBS 12.2 codeline can be found here:

• Oracle E-Business Suite 12.2.5 Readme (Doc ID 1983050.1)”

After going to edelivery.oracle.com:

Notice the Oracle Database 12.1.0.2 files with most of the ETCC patches already applied:

And, the Oracle Web Tier 11.1.1.9, software is already included. This makes updating to the latest Oracle Fusion Middleware much easier:

After downloading all the files, running a md5sum to make sure they all downloaded correctly, I staged the files according to: R12.2: How To Create the Stage In Preparation For Installation (Doc ID 1596433.1)

I followed the notes that are included below, but had some additional fixes, in order for the install to work correctly:
1) build the stage according to note 1596433.1
2) chmod -R 755 /home/stage
3) xhost +
4) Clean out /etc/oraInventory/ContentsXML/inventory.xml
5) fix /etc/oraInst.loc follow note 1292347.1
6) to fix the database installer, rapidwiz didn’t show the actual error.
I went to /home/stage/TechInstallMedia/databas/database and ran
runInstaller to get the errors and to run the fixup script. Then
rapidwiz would work.

Notes:
R12.2: How To Create the Stage In Preparation For Installation (Doc ID
1596433.1)
MD5 Checksums for R12.2 Rapid Install Media (Doc ID 1505510.1)
[INS-10002] Inventory Initialization Failed or [INS-10102] Installer
Initialization Failed during Installation (Doc ID 1292347.1)

Notes:
R12.2: How To Create the Stage In Preparation For Installation (Doc
ID 1596433.1)
MD5 Checksums for R12.2 Rapid Install Media (Doc ID 1505510.1)
[INS-10002] Inventory Initialization Failed or [INS-10102] Installer
Initialization Failed during Installation (Doc ID 1292347.1)