Outline Kubernetes infrastructure extensions

Change index page for infrastructure extensions: from autogenerated
to actual written text.

content/en/docs/concepts/extend-kubernetes/compute-storage-net/_index.md

@@ -1,4 +1,44 @@
 ---
 title: Compute, Storage, and Networking Extensions
 weight: 30
+no_list: true
 ---
+
+This section covers extensions to your cluster that do not come as part as Kubernetes itself.
+You can use these extensions to enhance the nodes in your cluster, or to provide the network
+fabric that links Pods together.
+
+* [CSI](/docs/concepts/storage/volumes/#csi) and [FlexVolume](/docs/concepts/storage/volumes/#flexvolume) storage plugins
+
+  {{< glossary_tooltip text="Container Storage Interface" term_id="csi" >}} (CSI) plugins
+  provide a way to extend Kubernetes with supports for new kinds of volumes. The volumes can
+  be backed by durable external storage, or provide ephemeral storage, or they might offer a
+  read-only interface to information using a filesystem paradigm.
+
+  Kubernetes also includes support for [FlexVolume](/docs/concepts/storage/volumes/#flexvolume)
+  plugins, which are deprecated since Kubernetes v1.23 (in favour of CSI).
+
+  FlexVolume plugins allow users to mount volume types that aren't natively
+  supported by Kubernetes. When you run a Pod that relies on FlexVolume
+  storage, the kubelet calls a binary plugin to mount the volume. The archived
+  [FlexVolume](https://git.k8s.io/design-proposals-archive/storage/flexvolume-deployment.md)
+  design proposal has more detail on this approach.
+
+  The [Kubernetes Volume Plugin FAQ for Storage Vendors](https://github.com/kubernetes/community/blob/master/sig-storage/volume-plugin-faq.md#kubernetes-volume-plugin-faq-for-storage-vendors)
+  includes general information on storage plugins.
+
+* [Device plugins](/docs/concepts/extend-kubernetes/compute-storage-net/device-plugins/)
+
+  Device plugins allow a node to discover new Node facilities (in addition to the
+  built-in node resources such as `cpu` and `memory`), and provide these custom node-local
+  facilities to Pods that request them.
+
+* [Network plugins](/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/)
+
+  A network plugin allow Kubernetes to work with different networking topologies and technologies.
+  Your Kubernetes cluster needs a _network plugin_ in order to have a working Pod network
+  and to support other aspects of the Kubernetes network model.
+
+  Kubernetes {{< skew currentVersion >}} is compatible with {{< glossary_tooltip text="CNI" term_id="cni" >}}
+  network plugins.
+