Operator condition available=False during upgrade (4.14.0-rc.7 to 4.15.0-0.nightly-2023-10-24-230302) with below error

status:
  conditions:
  - lastTransitionTime: "2023-10-25T02:05:07Z"
    message: Working towards 4.15.0-0.nightly-2023-10-24-230302
    status: "True"
    type: Progressing
  - lastTransitionTime: "2023-10-25T02:06:36Z"
    status: "False"
    type: Degraded
  - lastTransitionTime: "2023-10-25T02:05:54Z"
    message: 'Cluster not available for [{operator 4.14.0-rc.7}]: ControllerConfig.machineconfiguration.openshift.io
      "machine-config-controller" is invalid: [status.controllerCertificates[0].notAfter:
      Required value, status.controllerCertificates[0].notBefore: Required value,
      status.controllerCertificates[1].notAfter: Required value, status.controllerCertificates[1].notBefore:
      Required value, status.controllerCertificates[2].notAfter: Required value, status.controllerCertificates[2].notBefore:
      Required value, status.controllerCertificates[3].notAfter: Required value, status.controllerCertificates[3].notBefore:
      Required value, status.controllerCertificates[4].notAfter: Required value, status.controllerCertificates[4].notBefore:
      Required value, status.controllerCertificates[5].notAfter: Required value, status.controllerCertificates[5].notBefore:
      Required value, status.controllerCertificates[6].notAfter: Required value, status.controllerCertificates[6].notBefore:
      Required value, status.controllerCertificates[7].notAfter: Required value, status.controllerCertificates[7].notBefore:
      Required value, <nil>: Invalid value: "null": some validation rules were not
      checked because the object was invalid; correct the existing errors to complete
      validation]'
    reason: MachineConfigControllerFailed
    status: "False"
    type: Available
  - lastTransitionTime: "2023-10-25T02:06:43Z"
    message: One or more machine config pools are degraded, please see `oc get mcp`
      for further details and resolve before upgrading
    reason: DegradedPool
    status: "False"
    type: Upgradeable
  extension:
    master: 'pool is degraded because nodes fail with "2 nodes are reporting degraded
      status on sync": "Node ip-10-0-68-187.us-east-2.compute.internal is reporting:
      \"open /etc/docker/certs.d: no such file or directory\", Node ip-10-0-51-97.us-east-2.compute.internal
      is reporting: \"open /etc/docker/certs.d: no such file or directory\""'
    worker: all 2 nodes are at latest configuration rendered-worker-f9ff345da4f6740868e7238d5f820b65

Finally the upgrade can be completed successfully

4.15.0-0.nightly-2023-10-24-230302

upgrade cluster from 4.14 to 4.15 nightly

1. setup 4.14 cluster
2. upgrade the cluster to 4.15 nightly
3. during the upgrade check the operator status

Condition Available=False with validation error of controllerCertificates

No validation error

struct of ControllerCertificate in 4.14 branch

type ControllerCertificate struct {
	// subject is the cert subject
	Subject string `json:"subject"`

	// signer is the  cert Issuer
	Signer string `json:"signer"`

	// bundleFile is the larger bundle a cert comes from
	BundleFile string `json:"bundleFile"`
}

struct of ControllerCertificate in master branch (4.15)

type ControllerCertificate struct {
	// subject is the cert subject
	// +kubebuilder:validation:Required
	Subject string `json:"subject"`

	// signer is the  cert Issuer
	// +kubebuilder:validation:Required
	Signer string `json:"signer"`

	// notBefore is the lower boundary for validity
	// +kubebuilder:validation:Required
	NotBefore *metav1.Time `json:"notBefore"`

	// notAfter is the upper boundary for validity
	// +kubebuilder:validation:Required
	NotAfter *metav1.Time `json:"notAfter"`

	// bundleFile is the larger bundle a cert comes from
	// +kubebuilder:validation:Required
	BundleFile string `json:"bundleFile"`
}