How to import subledger journals

I want to import data created in an external system as subledger journals.
However, as far as I found, there does not seem to be an API and FBDI to register subledger journals.
If you know of any examples of automatically importing subledger journals from external systems to ERP, please let me know how to do it.

Is the only way to do this is to use ADFDI?

Regards.