Add warning when using NetworkPolicy with hostNetwork

Author: sfowl

modules/nw-networkpolicy-about.adoc

@@ -17,6 +17,11 @@ The Kubernetes `v1` NetworkPolicy features are available in {product-title}
 except for egress policy types and IPBlock.
 ====
 
+[WARNING]
+====
+`NetworkPolicy` rules do not apply to the host network namespace. Pods with host networking enabled are unaffected by `NetworkPolicy` rules.
+====
+
 By default, all Pods in a project are accessible from other Pods and network
 endpoints. To isolate one or more Pods in a project, you can create
 NetworkPolicy objects in that project to indicate the allowed incoming