Develop custom plugin

Hi
I would like to create my own custom plugin for Schema Registry, which will work with XML schemas. Can anyone help me to find some developer’s guide about create custom plugins for Schema Registry?

It’s not for XML, but does this help? Playing Chess with Confluent Schema Registry – Robert Yokota

Also, do you really need XML schema support directly in the registry? Kafka Connect Transforms will be able to convert into a supported format