Improve Kubeadm reference doc (#6103)

* automatically-generated kubeadm reference doc

* user-mantained kubeadm reference doc

docs/reference/setup-tools/kubeadm/kubeadm-config.md

@@ -0,0 +1,31 @@
+---
+approvers:
+- mikedanese
+- luxas
+- jbeda
+title: kubeadm config
+---
+{% capture overview %}
+Beginning with v1.8.0, kubeadm uploads the configuration of your cluster to a ConfigMap called 
+`kubeadm-config` in the `kube-system` namespace, and later reads the ConfigMap when upgrading. This enables correct configuration of system components, and provides a seamless user experience.
+
+You can use `kubeadm config view` to view the ConfigMap. If you initialized your cluster using kubeadm v1.7.x or lower, you can use `kubeadm config upload` to create a ConfigMap before you execute `kubeadm upgrade`.
+
+{% endcapture %}
+
+{% capture body %}
+## kubeadm config upload from-file {#cmd-config-from-file}
+{% include_relative generated/kubeadm_config_upload_from-file.md %}
+
+## kubeadm config upload from-flags {#cmd-config-from-flags}
+{% include_relative generated/kubeadm_config_upload_from-flags.md %}
+
+## kubeadm config view {#cmd-config-view}
+{% include_relative generated/kubeadm_config_view.md %}
+{% endcapture %}
+
+{% capture whatsnext %}
+* [kubeadm upgrade](kubeadm-upgrade.md) to upgrade a Kubernetes cluster to a newer version
+{% endcapture %}
+
+{% include templates/concept.md %}