Add DigitalOcean to cloud provider documentation.

Author: MorrisLaw

content/en/docs/concepts/cluster-administration/cloud-providers.md

@@ -125,6 +125,15 @@ If you wish to use the external cloud provider, its repository is [apache/clouds
 The CloudStack cloud provider uses the hostname of the node (as determined by the kubelet or overridden with `--hostname-override`) as the name of the Kubernetes Node object.
 Note that the Kubernetes Node name must match the CloudStack VM name.
 
+## DigitalOcean
+
+If you wish to use the external cloud provider, its repository is [digitalocean/digitalocean-cloud-controller-manager](https://github.com/digitalocean/digitalocean-cloud-controller-manager)
+
+### Node Name
+
+The DigitalOcean cloud provider uses the hostname of the node (as determined by the kubelet or overridden with `--hostname-override`) as the name of the Kubernetes Node object.
+Note that the Kubernetes Node name must match the DigitalOcean Droplet name.
+
 ## GCE
 
 If you wish to use the external cloud provider, its repository is [kubernetes/cloud-provider-gcp](https://github.com/kubernetes/cloud-provider-gcp#readme)