[libvirt] How to add custom tag to the libvirt xml file for a new feature of the VM

Hello, I am working on libvirt development and I wanted to add a custom tag to the libvirt xml to add a new feature to the VM. I am having trouble getting started with this. It would be really helpful if you can help me get started with this and guide me on what part of the source code that has to be modified to achieve the goal. Thanks in advance. Regards, Yashwanth KP