Selectively forward multicast between different networks

Network map:

  • OpenWrt wireless router with integrated switch.
    • Switch ports are in a bridge with IP 192.168.x.1/24. (I will call this network "X".) Net X hosts have internet access with default routes configured.
    • WIFI is a separate network with IP 192.168.y.1/24. (Network "Y"). Net Y does not have internet access. There is no packet forwarding, except a few static routes to specific hosts/ports in net X.
  • A computer in net Y with IP 192.168.y.10 uses multicast to detect network printers/scanners.
  • A multifunction printer/scanner in net X with IP 192.168.x.51 uses multicast to detect network computers to send scanned documents to them.
  • Various other devices in net X use multicast (TVs, players, etc.)

I want to give the computer in net Y access to printer in net X.
I did set up a static route for unicast traffic, but some of the printer functions, such as starting a scan from the printer's front panel, are not working. These functions rely on multicast traffic.

How do I selectively forward multicast traffic between the printer and the computer, without allowing the computer to "see" the other devices in net X that use multicast?

Thank you.