HDDS-3779. Add csi interface documents to show how to use ozone csi

hadoop-hdds/docs/content/interface/CSI.md

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+---
+title: CSI Protocol
+weight: 3
+summary: Ozone supports Container Storage Interface(CSI) protocol. You can use Ozone by mounting an Ozone volume by Ozone CSI.
+---
+
+<!---
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+
+`Container Storage Interface` (CSI) will enable storage vendors (SP) to develop a plugin once and have it work across a number of container orchestration (CO) systems.
+
+To get more information about CSI at [SCI spec](https://github.com/container-storage-interface/spec/blob/master/spec.md)
+
+Ozone CSI is an implementation of CSI, it can make possible of using Ozone as a storage volume for a container. 
+
+## Getting started
+
+First of all, we need an Ozone cluster with s3gateway, and its OM rpc port and s3gateway port must be visible to CSI pod,
+because CSIServer will access OM to create or delete a bucket, also, CSIServer will publish volume by creating a mount point to s3g
+through goofys. 
+
+If you don't have an Ozone cluster on kubernetes, you can reference [Kubernetes]({{< ref "start/Kubernetes.md" >}}) to create one. Use the resources from `kubernetes/examples/ozone` where you can find all the required Kubernetes resources to run cluster together with the dedicated Ozone CSI daemon (check `kubernetes/examples/ozone/csi`)   
+
+You should check if you already have a name of `/s3v` volume, if not create it by execute follow command:
+
+```bash
+kubectl exec -it  scm-0  bash
+[hadoop@scm-0 ~]$ ozone sh vol create s3v
+```
+
+Now, create the CSI related resources by execute the follow command.
+
+```bash
+kubectl create -f /ozone/kubernetes/examples/ozone/csi
+```
+
+## Crete pv-test and visit the result.
+
+Create pv-test related resources by execute the follow command.
+
+```bash
+kubectl create -f /ozone/kubernetes/examples/ozone/pv-test
+```
+
+Attach the pod scm-0 and put a key into the /s3v/pvc* bucket.
+
+```bash
+kubectl exec -it  scm-0  bash
+[hadoop@scm-0 ~]$ ozone sh bucket list s3v
+{
+  "metadata" : { },
+  "volumeName" : "s3v",
+  "name" : "pvc-861e2d8b-2232-4cd1-b43c-c0c26697ab6b",
+  "storageType" : "DISK",
+  "versioning" : false,
+  "creationTime" : "2020-06-11T08:19:47.469Z",
+  "encryptionKeyName" : null
+}
+[hadoop@scm-0 ~]$ ozone sh key put /s3v/pvc-861e2d8b-2232-4cd1-b43c-c0c26697ab6b/A LICENSE.txt
+```
+
+Now, let's forward port of the `ozone-csi-test-webserver-7cbdc5d65c-h5mnn` to see the UI through the web browser.
+
+```bash
+kubectl port-forward ozone-csi-test-webserver-7cbdc5d65c-h5mnn 8000:8000
+```
+
+Eventually, we can see the result from `http://localhost:8000/`
+
+![pvtest-webui](pvtest-webui.png)