Add docs (GKE part 8)

docs/book/src/topics/gke/cluster-upgrades.md

@@ -0,0 +1,5 @@
+# GKE Cluster Upgrades
+
+## Control Plane Upgrade
+
+Upgrading the Kubernetes version of the control plane is supported by the provider. To perform an upgrade you need to update the `controlPlaneVersion` in the spec of the `GCPManagedControlPlane`. Once the version has changed the provider will handle the upgrade for you.

docs/book/src/topics/gke/creating-a-cluster.md

@@ -0,0 +1,31 @@
+# Creating a GKE cluster
+
+New "gke" cluster templates have been created that you can use with `clusterctl` to create a GKE cluster.
+
+To create a GKE cluster with a managed node group (a.k.a managed machine pool):
+
+```bash
+clusterctl generate cluster capi-gke-quickstart --flavor gke --worker-machine-count=3 > capi-gke-quickstart.yaml
+```
+
+## Kubeconfig
+
+When creating an GKE cluster 2 kubeconfigs are generated and stored as secrets in the management cluster.
+
+### User kubeconfig
+
+This should be used by users that want to connect to the newly created GKE cluster. The name of the secret that contains the kubeconfig will be `[cluster-name]-user-kubeconfig` where you need to replace **[cluster-name]** with the name of your cluster. The **-user-kubeconfig** in the name indicates that the kubeconfig is for the user use.
+
+To get the user kubeconfig for a cluster named `managed-test` you can run a command similar to:
+
+```bash
+kubectl --namespace=default get secret managed-test-user-kubeconfig \
+   -o jsonpath={.data.value} | base64 --decode \
+   > managed-test.kubeconfig
+```
+
+### Cluster API (CAPI) kubeconfig
+
+This kubeconfig is used internally by CAPI and shouldn't be used outside of the management server. It is used by CAPI to perform operations, such as draining a node. The name of the secret that contains the kubeconfig will be `[cluster-name]-kubeconfig` where you need to replace **[cluster-name]** with the name of your cluster. Note that there is NO `-user` in the name.
+
+The kubeconfig is regenerated every `sync-period` as the token that is embedded in the kubeconfig is only valid for a short period of time.

docs/book/src/topics/gke/disabling.md

@@ -0,0 +1,3 @@
+# Disabling GKE Support
+
+Support for GKE is disabled by default when you use the GCP infrastructure provider.

docs/book/src/topics/gke/enabling.md

@@ -0,0 +1,8 @@
+# Enabling GKE Support
+
+Enabling GKE support is done via the **GKE** feature flag by setting it to true. This can be done before running `clusterctl init` by using the **EXP_CAPG_GKE** environment variable:
+
+```shell
+export EXP_CAPG_GKE=true
+clusterctl init --infrastructure gcp
+```

docs/book/src/topics/gke/index.md

@@ -0,0 +1,27 @@
+# GKE Support in the GCP Provider
+
+- **Feature status:** Experimental
+- **Feature gate (required):** GKE=true
+
+## Overview
+
+The GCP provider supports creating GKE based cluster. Currently the following features are supported:
+
+- Provisioning/managing a GCP GKE Cluster
+- Upgrading the Kubernetes version of the GKE Cluster
+- Creating a managed node pool and attaching it to the GKE cluster
+
+The implementation introduces the following CRD kinds:
+
+- GCPManagedCluster - presents the properties needed to provision and manage the general GCP operating infrastructure for the cluster (i.e project, networking, iam)
+- GCPManagedControlPlane - specifies the GKE Cluster in GCP and used by the Cluster API GCP Managed Control plane
+- GCPManagedMachinePool - defines the managed node pool for the cluster
+
+And a new template is available in the templates folder for creating a managed workload cluster.
+
+## SEE ALSO
+
+* [Enabling GKE Support](enabling.md)
+* [Disabling GKE Support](disabling.md)
+* [Creating a cluster](creating-a-cluster.md)
+* [Cluster Upgrades](cluster-upgrades.md)