- Allowed setting the `hostnameOverride` field in `PodSpec` to specify any RFC 1123 DNS subdomain as the pod's hostname. The `HostnameOverride` feature gate was introduced to control enablement of this functionality. ([#132558](https://github.com/kubernetes/kubernetes/pull/132558), [@HirazawaUi](https://...

- `PodSchedulingReadiness` is graduated to beta. ([#115815](https://github.com/kubernetes/kubernetes/pull/115815), [@Huang-Wei](https://github.com/Huang-Wei))
- `PodSpec.Container.Resources` became mutable for CPU and memory resource types.
  - `PodSpec.Container.ResizePolicy` (new object) gives users control over how their containers are resized.
  - `PodStatus.Resize` status describes the state of a requested Pod resize.

- Add scheduling support for RuntimeClasses. RuntimeClasses can now specify nodeSelector constraints & tolerations, which are merged into the PodSpec for pods using that RuntimeClass. ([#80825](https://github.com/kubernetes/kubernetes/pull/80825), [@tallclair](https://github.com/tallclair))

- Enabled in-place resizing of pod-level resources.  
  - Added `Resources` in `PodStatus` to capture resources set in the pod-level cgroup.  
  - Added `AllocatedResources` in `PodStatus` to capture resources requested in the `PodSpec`. ([#132919](https://github.com/kubernetes/kubernetes/pull/132919), [@ndixita](https://github.com/ndixita)) [SIG API Machinery, Apps, Architecture, Auth, CLI, Instrumentation, Node, Scheduling and Testing]

- kubeadm: make sure the extra environment variables written to a kubeadm managed PodSpec are sorted alpha-numerically by the environment variable name. ([#126743](https://github.com/kubernetes/kubernetes/pull/126743), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

* Bump GCE ContainerVM to container-vm-v20170627 ([#48159](https://github.com/kubernetes/kubernetes/pull/48159), [@zmerlynn](https://github.com/zmerlynn))
* Add PriorityClassName and Priority fields to PodSpec. ([#45610](https://github.com/kubernetes/kubernetes/pull/45610), [@bsalamat](https://github.com/bsalamat))

### API Change

- Add `NodeInclusionPolicy` to `TopologySpreadConstraints` in PodSpec. ([#108492](https://github.com/kubernetes/kubernetes/pull/108492), [@kerthcet](https://github.com/kerthcet))

- Removed note that `hostAliases` are not supported on hostNetwork Pods from the PodSpec API. The feature has been supported since v1.8. ([#122422](https://github.com/kubernetes/kubernetes/pull/122422), [@neolit123](https://github.com/neolit123))