int iommu_device_register_bus(struct iommu_device *iommu,
			      const struct iommu_ops *ops, struct bus_type *bus,
			      struct notifier_block *nb)
int iommu_device_register_bus(struct iommu_device *iommu,
			      const struct iommu_ops *ops,
			      const struct bus_type *bus,
			      struct notifier_block *nb)