VOIP and IPTV VLANs on separate physical ports

Yes, for simple cases like this, you can leave the switch configuration alone.

In LuCI under Interfaces → lan → Physical settings, uncheck eth2.

OK, in that case you will have to make the traffic between eth2 and internal switch tagged and deploy both VLANs on the switch. So in switch config, add a new vlan similar to the 243. Select different physical port to which your IP phone is connected to. This port should be untagged and present only in this one VLAN. Then, swhich port6 on both vlans 243 and 237 to tagged mode. The interfaces in the bridge will then be eth2.237 and eth2.243.

See the image (and the erratum) in this post. Simply port 0 - 4 are connected to the physical sockets, port 5 (nicknamed as CPU in LuCI) is connected to eth0 and port 6 is connected to eth2.