This seems to be non-standart, but it is implemented by all the execution clients, see: https://github.com/search?q=repo%3Aethereum%2Fhive%20admin_nodeInfo&type=code

Here is more info about the endpoint.
https://geth.ethereum.org/docs/interacting-with-geth/rpc/ns-admin#admin-nodeinfo

This seems to be necessary for the Hive P2P simulation tests