driver core: Add iommu_group tracking to struct device IOMMU groups allow IOMMU drivers to represent DMA visibility and isolation of devices. Multiple devices may be grouped together for the purposes of DMA. Placing a pointer on struct device enable easy access for things like streaming DMA programming and drivers like VFIO. Signed-off-by: Alex Williamson Acked-by: Greg Kroah-Hartman Acked-by: Benjamin Herrenschmidt Signed-off-by: Joerg Roedel ƒ… q”