The external network providers API feature, and its use cases, must be documented. In RHV 4.0, changes have been made to the existing OpenStack Network provider functionality to allow users to add any external networking provider that implements the OpenStack Neutron API. The Manager uses the REST API to communicate with external network management systems, and use the networks defined in them in provisioned virtual machines. The feature also adds a "read-only" feature to network providers. This prevents the user from changing the provider from oVirt. No networks or subnets can be added/modified/deleted.
Related section: https://access.redhat.com/documentation/en/red-hat-virtualization/4.0-beta/administration-guide/112-adding-external-providers
Documentation Link: https://access.redhat.com/documentation/en/red-hat-virtualization/4.0/paged/administration-guide/chapter-11-external-providers