Document additionalNetworks and additional_security_group parameters

docs/user/openstack/customization.md

@@ -10,6 +10,8 @@ Beyond the [platform-agnostic `install-config.yaml` properties](../customization
   * [Minimal](#minimal)
   * [Custom-machine-pools](#custom-machine-pools)
 * [Image Overrides](#image-overrides)
+* [Additional Networks](#additional-networks)
+* [Additional Security Groups](#additional-security-groups)
 * [Further customization](#further-customization)
 
 ## Cluster-scoped properties
@@ -119,6 +121,64 @@ platform:
       clusterOSImage: my-rhcos
 ```
 
+## Additional Networks
+
+You can set additional networks for your machines by defining `additionalNetworks` parameter in the machine configuration. The parameter is a list of objects that contain a network `uuid`:
+
+```yaml
+additionalNetworks:
+- uuid: <network1_uuid>
+- uuid: <network2_uuid>
+```
+
+You can attach this parameter for both `controlPlane` and `compute` machines:
+
+Example:
+
+```yaml
+compute:
+- name: worker
+  platform:
+    openstack:
+      additionalNetworks:
+      - uuid: fa806b2f-ac49-4bce-b9db-124bc64209bf
+controlPlane:
+  name: master
+  platform:
+    openstack:
+      additionalNetworks:
+      - uuid: fa806b2f-ac49-4bce-b9db-124bc64209bf
+```
+
+## Additional Security Groups
+
+You can set additional security groups for your machines by defining `additionalSecurityGroups` parameter in the machine configuration. The parameter is a list of strings with additional security group names:
+
+```yaml
+additionalSecurityGroups:
+- <security_group1_name>
+- <security_group2_name>
+```
+
+You can attach this parameter for both `controlPlane` and `compute` machines:
+
+Example:
+
+```yaml
+compute:
+- name: worker
+  platform:
+    openstack:
+      additionalSecurityGroups:
+      - additional_security_group
+controlPlane:
+  name: master
+  platform:
+    openstack:
+      additionalSecurityGroups:
+      - additional_security_group
+```
+
 ## Further customization
 
 For customizing the installation beyond what is possible with `openshift-install`, refer to the [UPI (User Provided Infrastructure) documentation](./install_upi.md).