Register subscribe handler for custom event

[terraformer]

Hello, I’ve read pjsip.conf documentation, searched the wiki and the web but still have no clue how to subscribe to a custom event.
I have a Yealink T48s and configured one line as SCA. When I pickup the line, the phone sends a SUBSCRIBE message with Event: line-seize. Asterisk response with

WARNING[4662]: res_pjsip_pubsub.c:787 subscription_get_handler_from_rdata: No registered subscribe handler for event line-seize

Ho do I register a subscribe handler? Did I just miss a hint-extension?
Is there any way to handle this kind of event? Or do I have to code my own line-seize module?
Thanks

[jcolp]

There is no support for such an event. An Asterisk C module would have to be written to handle it.

[terraformer]

Dear @jcolp, thank you! Then I think I already stumbled upon the description on how to do that.
Thanks & best!