Here is a new thing I found out about database processes. If you read my post about listener registration you know about the communication between the database and the listener when using dynamic registration.
As I wrote in the post, PMON is the process that is responsible for the communication with the listener. Apparently, starting with Oracle 12c, Oracle created a new process called LREG. This is a new mandatory process (just like DBWR, LGWR, CKPT, PMON and others) and it is now responsible for the communication with the listener and the dynamic registration process.
You can find information about it in the documentation, click here.