apiVersion: operator.openshift.io/v1
kind: IngressController
metadata:
  name: default
  namespace: openshift-ingress-operator
spec:
  replicas: 2
  logging:
    access:
      destination:
        type: Syslog
        syslog:
          address: 1.2.3.4  <------
          port: 10514

This then requires a change to the HA Proxy configuration with the new IP Address and as such a restart of the service potentially disrupting traffic.

It would be more beneficial to configure a DNS Name such as the name of the Service rather than the IP Address.  

Define the value or impact to you or the business
We could lose the ability to forward logs to an external log store if the internal service IP Address changes and the HA Proxy is not re-configured wit the new IP Address.

 ingresscontrollers.operator.openshift.io "default" was not valid:
# * <nil>: Invalid value: "": "spec.logging.access.destination.syslog" must validate one and only one schema (oneOf). Found none valid
# * spec.logging.access.destination.syslog.address: Invalid value: "syslog-ng.test.svc.cluster.local": spec.logging.access.destination.syslog.address in body must be of type ipv4: "syslog-ng.test.svc.cluster.local"

  logging:
    access:
      destination:
        syslog:
          address: syslog-ng.test.svc.cluster.local
          maxLength: 1024
          port: 6514
        type: Syslog
      logEmptyRequests: Log

Changing the address to be an IP works