The converter and the solar charge controller (which goes between the panel and the battery) are both battery chargers and can be on the battery in parallel with each other.
BUT you can't feed the battery with the controller by going through the converter. And you can't go through the controller with the converter.
So some set-ups have the converter feeding a fuse panel which has battery wire lugs on the panel too so either the battery or the converter can feed 12v to those fused circuits, and the converter also has a path to the battery via those lugs they share. Now you can add the solar controller's battery wires to those lugs too.
Only trouble with that is
-if the batteries are disconnected for some reason, the solar can supply those 12v circuits, which is a no-no with solar controllers that say only run a load with a battery connected, and
-your controller might end up being too far from the battery (although usually the DC fuse panel-battery wire will have fat enough wire so it can take the converter's higher (than the controller's) amps.