Welcome to the Community - You have two options:
- Provide a pass through to the serial port on your physical host which of course means you will not be able to take advactage of vmotion, DRS, or HA -
- Get an IP based serial port from a company like DIgi which will allow you to provide the VM the serial port over the IP network and as long as the hosts can see the device vmotion, DRS and HA will work