code: func ValidateJoinControlPlane(c *kubeadm.JoinControlPlane, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  	if c != nil {
  		allErrs = append(allErrs, ValidateAPIEndpoint(&c.LocalAPIEndpoint, fldPath.Child("localAPIEndpoint"))...)
  	}
  	return allErrs
  }
docs: // ValidateJoinControlPlane validates joining control plane configuration and collects all encountered errors