IBM i (AS/400) support for Ghidra.
Writeup: Below MI - IBM i for Hackers
Kaitai structure definition for the Loader: PGM-Kaitai
Just like with every Ghidra extension, you build using Gradle:
$ export GHIDRA_INSTALL_DIR=/path/to/ghidra
$ gradle buildExtension
This will generate a .zip in build/dist, you should add this file as an extension to Ghidra.
The Loader part should be able to recognize serialized *PGMs and associate them with the new POWER AS Processor language. The Analyzer part will do some initial function recognizion based on entry points defined in the file structure.