Need to have the same release note in 4.14 docs as 4.15 concerning the "Open Virtual Network Infrastructure Controller default range". The text is below directly from 4.15 release notes: 

Open Virtual Network Infrastructure Controller default range

Previously, the IP address range 168.254.0.0/16 was the default IP address range that the Open Virtual Network Infrastructure Controller used for the transit switch subnet. With this update, the Controller uses 100.88.0.0/16 as the default IP address range. Do not use this IP range in your production infrastructure network. (OCPBUGS-20178)

https://docs.openshift.com/container-platform/4.15/release_notes/ocp-4-15-release-notes.html

    4.14 only.  You can't upgrade to later (4.15+) versions if you have overlapping subnet ranges issues so no need to report it in later versions

    We already have a good note in the migration section of the document about this at https://docs.openshift.com/container-platform/4.14/networking/ovn_kubernetes_network_provider/migrate-from-openshift-sdn.html#considerations-migrating-ovn-kubernetes-network-provider_migrate-from-openshift-sdn.  It says: 

"OVN-Kubernetes, the default network provider in OpenShift Container Platform 4.14 and later versions, uses the following IP address ranges internally: 100.64.0.0/16, 169.254.169.0/29, 100.88.0.0/16, fd98::/64, fd69::/125, and fd97::/64. If your cluster uses OVN-Kubernetes, do not include any of these IP address ranges in any other CIDR definitions in your cluster or infrastructure."

We just need to make sure its in the release notes too to raise visibility