kubeadm ports updates (kubernetes#8886)

* disable the kubelet readonly port

* add doc for required port source

Author: dixudx

content/en/docs/tasks/tools/install-kubeadm.md

@@ -52,22 +52,20 @@ route, we recommend you add IP route(s) so Kubernetes cluster addresses go via t
 
 ### Master node(s)
 
-| Protocol | Direction | Port Range | Purpose                 |
-|----------|-----------|------------|-------------------------|
-| TCP      | Inbound   | 6443*      | Kubernetes API server   |
-| TCP      | Inbound   | 2379-2380  | etcd server client API  |
-| TCP      | Inbound   | 10250      | Kubelet API             |
-| TCP      | Inbound   | 10251      | kube-scheduler          |
-| TCP      | Inbound   | 10252      | kube-controller-manager |
-| TCP      | Inbound   | 10255      | Read-only Kubelet API   |
+| Protocol | Direction | Port Range | Purpose                 | Used By                   |
+|----------|-----------|------------|-------------------------|---------------------------|
+| TCP      | Inbound   | 6443*      | Kubernetes API server   | All                       |
+| TCP      | Inbound   | 2379-2380  | etcd server client API  | kube-apiserver, etcd      |
+| TCP      | Inbound   | 10250      | Kubelet API             | Self, Control plane       |
+| TCP      | Inbound   | 10251      | kube-scheduler          | Self                      |
+| TCP      | Inbound   | 10252      | kube-controller-manager | Self                      |
 
 ### Worker node(s)
 
-| Protocol | Direction | Port Range  | Purpose               |
-|----------|-----------|-------------|-----------------------|
-| TCP      | Inbound   | 10250       | Kubelet API           |
-| TCP      | Inbound   | 10255       | Read-only Kubelet API |
-| TCP      | Inbound   | 30000-32767 | NodePort Services**   |
+| Protocol | Direction | Port Range  | Purpose               | Used By                 |
+|----------|-----------|-------------|-----------------------|-------------------------|
+| TCP      | Inbound   | 10250       | Kubelet API           | Self, Control plane     |
+| TCP      | Inbound   | 30000-32767 | NodePort Services**   | All                     |
 
 ** Default port range for [NodePort Services](/docs/concepts/services-networking/service/).