Describe the changes in the doc and link to your dev story:

The current documentation provides the steps to replace control plane nodes from UI.
https://docs.redhat.com/en/documentation/red_hat_advanced_cluster_management_for_kubernetes/2.12/html-single/clusters/index#adding-ctrl-nodes-managed

However, For customers who prefers API orver UI below steps can be followed to achieve the same task.

1. Login to the Hub cluster:

$ oc login --token=sha256~value--server=https://api.clustername.basedomain:6443

2. Boot the machine that you want to use as a master node from the ISO you previously downloaded.

3. Check agent state to make sure it's ready to be bound to the cluster again

$oc project host-inventory-namespace
$oc get agent <name of agent> -oyaml | grep state
E.g.
$ oc get agent -oyaml c6e00642-0e11-1689-a79d-0e131d2c6ecf | grep state
    agent.agent-install.openshift.io/state: known-unbound
    state: known-unbound
    stateInfo: Host is ready to be bound to a cluster

4. Patch agent to be approved with master role

oc patch agent c6e00642-0e11-1689-a79d-0e131d2c6ecf -p '{"spec":{"approved":true,"role":"master"}}' --type=merge

5. Verify patch

$ oc get agent
NAME                                   CLUSTER    APPROVED   ROLE     STAGE
060c0642-f24e-d216-50ff-6c7ab5848eb5   hcpagent   true       master   Done
776b0642-f810-0a12-574c-2bd60a25a392   hcpagent   true       worker   Done
9fec0642-7d7d-b2f3-192e-9c40e6bdb596   hcpagent   true       worker   Done
c6e00642-0e11-1689-a79d-0e131d2c6ecf              true       master
fbd70642-dbfd-e7c4-a149-7635e7b9d67b   hcpagent   true       master   Done

6. Add (bind) agent to cluster

oc patch agent c6e00642-0e11-1689-a79d-0e131d2c6ecf -p '{"spec":{"clusterDeploymentName":{"name":"hcpagent","namespace":"hcpagent"}}
}' --type=merge

6. Confirm agent is bound to cluster

$ oc get agent
NAME                                   CLUSTER    APPROVED   ROLE     STAGE
060c0642-f24e-d216-50ff-6c7ab5848eb5   hcpagent   true       master   Done
776b0642-f810-0a12-574c-2bd60a25a392   hcpagent   true       worker   Done
9fec0642-7d7d-b2f3-192e-9c40e6bdb596   hcpagent   true       worker   Done
c6e00642-0e11-1689-a79d-0e131d2c6ecf   hcpagent   true       master
fbd70642-dbfd-e7c4-a149-7635e7b9d67b   hcpagent   true       master   Done

7. Wait for agent to install

oc get agent -w

1. - [ ] Mandatory: Add the required version to the Fix version/s field.

2.12

2. - [ ] Mandatory: Choose the type of documentation change or review.

• [ ] We need to add a new document to an existing section

3. - [ ] Mandatory: Find the link to where the documentation update
should go and add it to the recommended changes. You can either use the
published doc or the staged repo for this step:

Note: As the feature and doc is understood, this recommendation may
change. If this is new documentation, link to the section where you think
it should be placed.

Customer Portal published version

https://docs.redhat.com/en/documentation/red_hat_advanced_cluster_management_for_kubernetes/2.12

Need to update the following section:
https://docs.redhat.com/en/documentation/red_hat_advanced_cluster_management_for_kubernetes/2.12/html-single/clusters/index#adding-ctrl-nodes-managed

Doc staged repo within the ACM Workspace:
https://github.com/stolostron/rhacm-docs

4. - [ ] Mandatory for GA content:

• [ ] Add steps, the diff, known issue, and/or other important
  conceptual information in the following space:

• steps as mentioned above

• [ ] *Add Required access level *(example, *Cluster
  Administrator*) for the user to complete the task:

• Cluster Administrator access required.

5. - [ ] Mandatory for bugs: What is the diff? Clearly define what the
problem is, what the change is, and link to the current documentation. Only
use this for a documentation bug.