The parent module calls all child modules and it's where we define input variables if required by a child module.

AzurePolicyRootModuleExample.tf

module "policy_assignments" {
  source = "./modules/policy-assignments"

  tag_governance_policyset_id             = "${module.policyset_definitions.tag_governance_policyset_id}"
  iam_governance_policyset_id             = "${module.policyset_definitions.iam_governance_policyset_id}"
  security_governance_policyset_id        = "${module.policyset_definitions.security_governance_policyset_id}"
  data_protection_governance_policyset_id = "${module.policyset_definitions.data_protection_governance_policyset_id}"
}