In RHDEVDOCS-2605, an example for sending logs to several kafka brokers was added to the documentation, but the change is missing from 4.8 docs. It seems the "module" in the PR (the example for 4.12 is in [1]) is referenced in 4.6 and 4.7 docs [2], but removed from newer releases [3].

[1] https://github.com/openshift/openshift-docs/blame/enterprise-4.12/modules/cluster-logging-collector-log-forward-kafka.adoc
[2] https://github.com/openshift/openshift-docs/blame/enterprise-4.7/logging/cluster-logging-external.adoc#L37
[3] https://github.com/openshift/openshift-docs/commit/ce5adee99992ad3322b5bc2642c714021fdff785#diff-a9d6b59b49e95b71da4ec7a0e6c9616904b4eb649654f74b5e1bbf906da09e82L36