add documentation for running knative on IBM s390x/IBM ppc64le platfo…

…rms (#6043)

* added documentation to configure network for s390x

* adding authentication details for redhat catalog

* chore: updated review comments

* corrected allignment

* corrected alignment

* fix indentations

* Apply suggestions from code review

Co-authored-by: David Hadas <david.hadas@gmail.com>

* corrected intendetion in file

* correct allignment in file

* Update docs/install/yaml-install/serving/install-serving-with-yaml-on-IBM-Z-and-IBM-P.md

---------

Co-authored-by: David Hadas <david.hadas@gmail.com>

docs/install/yaml-install/serving/install-serving-with-yaml-on-IBM-Z-and-IBM-P.md

@@ -0,0 +1,22 @@
+# Install a networking layer on IBM Z and IBM Power platforms
+
+This additional step is required for installing the Kourier networking layer on IBM Z and IBM Power platforms.
+
+Once you completed installing Kourier,  patch the envoy image as described below. Use the envoy image included as part of the [RedHat Maistra](https://maistra.io/) distribution. Maistra is an opinionated distribution of Istio designed to work with OpenShift and is supported on IBM Z and IBM Power platforms.
+
+1. Find the image name to use:  
+    1. Access the [redhat catalog](https://catalog.redhat.com/software/containers/openshift-service-mesh/proxyv2-rhel8/5d2cda455a134672890f640a) 
+    2.  Choose the appropriate architecture (ppc64le/s390x) from the architecture drop down. 
+    3. Choose the latest tag from the list of available tags at the tag dropdown.
+    4. Click on the "get this image" tab and copy the image name. For example: `registry.redhat.io/openshift-service-mesh/proxyv2-rhel8@sha256:ced904...`
+
+2. Patch the **3scale-kourier-gateway**  deployment in **kourier-system** namespace with latest available image using **kubectl** as shown below.
+
+  ```bash
+    kubectl patch deployment 3scale-kourier-gateway -n kourier-system -p \
+    '{"spec":{"template":{"spec":{"containers":[{"name":"kourier-gateway" "image":"<the proxyv2 image name>"}]}}}}'
+  ```
+
+!!! note
+    1. If there are authentication issues, create [redhat developer account](developers.redhat.com/register) to pull images from redhat catalog. 
+    2. Please refer to the page to [configure pull secrets](https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/#add-imagepullsecrets-to-a-service-account)

docs/install/yaml-install/serving/install-serving-with-yaml.md

@@ -29,6 +29,10 @@ To install the Knative Serving component:
 The following tabs expand to show instructions for installing a networking layer.
 Follow the procedure for the networking layer of your choice:
 
+!!! note
+    **Only Kourier network plugin supported for IBM Z and IBM Power platform.** 
+    Follow the below steps to install Kourier. Post installation, patch the envoy image based on RedHat Maistra as described in [this link](./install-serving-with-yaml-on-IBM-Z-and-IBM-P.md).
+
 <!-- TODO: Link to document/diagram describing what is a networking layer.  -->
 <!-- This indentation is important for things to render properly. -->