kind: CustomResourceDefinition
apiVersion: apiextensions.k8s.io/v1beta1
metadata:
  name: runtimeclasses.node.k8s.io
  labels:
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  group: node.k8s.io
  version: v1alpha1
  versions:
    - name: v1alpha1
      served: true
      storage: true
  names:
    plural:   runtimeclasses
    singular: runtimeclass
    kind:     RuntimeClass
  scope: Cluster
  validation:
    openAPIV3Schema:
      properties:
        spec:
          properties:
            runtimeHandler:
              type: string
              pattern: '^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$'

kind: CustomResourceDefinition
apiVersion: apiextensions.k8s.io/v1beta1
metadata:
  name: runtimeclasses.node.k8s.io
  labels:
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  group: node.k8s.io
  version: v1alpha1
  versions:
    - name: v1alpha1
      served: true
      storage: true
  names:
    plural:   runtimeclasses
    singular: runtimeclass
    kind:     RuntimeClass
  scope: Cluster
  validation:
    openAPIV3Schema:
      properties:
        spec:
          properties:
            runtimeHandler:
              type: string
              pattern: '^([a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*)?$'

Allow an empty "" runtimeHandler
Allow an empty "" runtimeHandler
