RFXtrx433XL USB HA controller with P1 DSMR


I have a setup with a RFXtrx433XL which works fine.

The XL version of the RFXcom transceiver has a P1 option to read smart meters (DSMR).
I tried to configure the DSMR plugin but it does not look like it is going to work in the way the DSMR read plugin does with directly connecting to the RFXcom usb port.
WIth the RFXcom tool data is coming from the P1 port. So data is read.

Since I am new into Hass I would like to know if someone can point me in the right direction where to start with debugging the data and how to read the RFXtrx for P1 data.