Plugin 2.4 creation or convertion from 2.1

Hello everyone.

I'm installing OCS Inventory NG 2.4.1 and I'd like to migrate some custom plugin that we have on version 2.1.1.

Unfortunately I'm not able to find a guide for create a plugin 2.4 from scratch or to upgrade an old one.

Anybody has some ideas or hint?

Thank you for your help.