update docs to include os version upgrade messaging

Signed-off-by: Rahul Ganesh <[email protected]>

docs/content/en/docs/clustermgmt/cluster-upgrades/baremetal-upgrades.md

@@ -170,8 +170,7 @@ spec:
       ...
 ```
 
->**_NOTE:_** If you have a custom machine image for your nodes in your cluster config yaml you may also need to update 
-your [`TinkerbellDatacenterConfig`]({{< relref "../../getting-started/baremetal/bare-spec/#tinkerbelldatacenterconfig-fields" >}}) with a new [`osImageURL`]({{< relref "../../getting-started/baremetal/bare-spec/#osimageurl" >}}).
+>**_NOTE:_** If you have a custom machine image for your nodes in your cluster config yaml or to upgrade a node or group of nodes to a new operating system version (ie. RHEL 8.7 to RHEL 8.8), you may also need to update your [`TinkerbellDatacenterConfig`]({{< relref "../../getting-started/baremetal/bare-spec/#tinkerbelldatacenterconfig-fields" >}}) or [`TinkerbellMachineConfig`]({{< relref "../../getting-started/baremetal/bare-spec/#tinkerbellmachineconfig-fields" >}}) with the new operating system image URL [`osImageURL`]({{< relref "../../getting-started/baremetal/bare-spec/#osimageurl" >}}). 
 
 and then you will run the [upgrade cluster command]({{< relref "baremetal-upgrades/#upgrade-cluster-command" >}}).
 
@@ -269,6 +268,7 @@ and then you will run the [upgrade cluster command]({{< relref "baremetal-upgrad
 
 `Cluster`:
 - `kubernetesVersion`
+- `workerNodeGroupConfigurations.kubernetesVersion`
 
 ### Advanced configuration for rolling upgrade
 

docs/content/en/docs/getting-started/baremetal/bare-spec.md

@@ -199,6 +199,11 @@ EKS Anywhere will add by default.
 Modifying the labels associated with a worker node group configuration will cause new nodes to be rolled out, replacing
 the existing nodes associated with the configuration.
 
+### workerNodeGroupConfigurations.kubernetesVersion
+The Kubernetes version you want to use for this worker node group. [Supported values]({{< relref "../../concepts/support-versions/#kubernetes-support" >}}): `1.28`, `1.27`, `1.26`, `1.25`, `1.24`
+
+Must be less than or equal the cluster `kubernetesVersion`. There can only be a skew of two minor versions between the control plane and each worker node. Removing `workerNodeGroupConfiguration.kubernetesVersion` will trigger an upgrade to that node group to upgrade to the root level kubernetesVersion.
+
 ## TinkerbellDatacenterConfig Fields
 
 ### tinkerbellIP
@@ -209,7 +214,7 @@ When separate management and workload clusters are supported in Bare Metal, the
 
 ### osImageURL
 Optional field to replace the default Bottlerocket operating system. EKS Anywhere can only auto-import Bottlerocket. In order to use Ubuntu or RHEL see [building baremetal node images]({{< relref "../../osmgmt/artifacts/#build-bare-metal-node-images" >}})
-to learn more on building and using Ubuntu with an EKS Anywhere cluster. This field is also useful if you want to provide a customized operating system image or simply host the standard image locally.
+to learn more on building and using Ubuntu with an EKS Anywhere cluster. This field is also useful if you want to provide a customized operating system image or simply host the standard image locally. To upgrade a node or group of nodes to a new operating system version (ie. RHEL 8.7 to RHEL 8.8), modify this field to point to the new operating system image URL and run [upgrade cluster command]({{< relref "../../clustermgmt/cluster-upgrades/baremetal-upgrades/#upgrade-cluster-command" >}}).
 
 ### hookImagesURLPath
 Optional field to replace the HookOS image.
@@ -263,7 +268,7 @@ Operating system on the machine. Permitted values: `bottlerocket`, `ubuntu`, `re
 
 ### osImageURL (optional)
 Optional field to replace the default Bottlerocket operating system. EKS Anywhere can only auto-import Bottlerocket. In order to use Ubuntu or RHEL see [building baremetal node images]({{< relref "../../osmgmt/artifacts/#build-bare-metal-node-images" >}})
-to learn more on building and using Ubuntu with an EKS Anywhere cluster. This field is also useful if you want to provide a customized operating system image or simply host the standard image locally.
+to learn more on building and using Ubuntu with an EKS Anywhere cluster. This field is also useful if you want to provide a customized operating system image or simply host the standard image locally. To upgrade a node or group of nodes to a new operating system version (ie. RHEL 8.7 to RHEL 8.8), modify this field to point to the new operating system image URL and run [upgrade cluster command]({{< relref "../../clustermgmt/cluster-upgrades/baremetal-upgrades/#upgrade-cluster-command" >}}).
 
 >**_NOTE:_** If specified for a single `TinkerbellMachineConfig`, osImageURL has to be specified for all the `TinkerbellMachineConfigs`.
 osImageURL field cannot be specified both in the `TinkerbellDatacenterConfig` and `TinkerbellMachineConfig` objects.