Added 1.6 Upgrade notes to outline changes for etcd 3.

docs/admin/cluster-management.md

@@ -19,7 +19,9 @@ To install Kubernetes on a set of machines, consult one of the existing [Getting
 
 ## Upgrading a cluster
 
-The current state of cluster upgrades is provider dependent.
+The current state of cluster upgrades is provider dependent, and some releases may require special care when upgrading. It is recommended that administrators consult both the [release notes](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG.md), as well as the version specific upgrade notes prior to upgrading their clusters.  
+
+* [Upgrading to 1.6](/docs/admin/upgrade)
 
 ### Upgrading Google Compute Engine clusters
 
@@ -56,8 +58,12 @@ The node upgrade process is user-initiated and is described in the [GKE document
 
 ### Upgrading clusters on other platforms
 
-The `cluster/kube-push.sh` script will do a rudimentary update.  This process is still quite experimental, we
-recommend testing the upgrade on an experimental cluster before performing the update on a production cluster.
+Different providers, and tools, will manage upgrades differently.  It is recommended that you consult their main documentation regarding upgrades. 
+
+* [kops](https://github.com/kubernetes/kops)
+* [kargo](https://github.com/kubernetes-incubator/kargo)
+* [CoreOS Tectonic](https://coreos.com/tectonic/docs/latest/admin/upgrade.html)
+* ... 
 
 ## Resizing a cluster