If you want to integrate the camera into milestone, you will need to have a dedicated driver for the camera in Recording Server.
Or if there is not any driver for the camera, you can develop your own driver using Driver Framework.
Please check if the camera is supported by Milestone here –
https://www.milestonesys.com/community/business-partner-tools/supported-devices/
If you want to integrate your own driver, the following link might be helpful for you –
Introduction to the MIP Driver Framework
3rd Party Driver Test Tool guide