This is a pretty significant milestone for anyone interested in running Linux on Apple Silicon.

The Asahi Linux work around Apple's proprietary ACIO subsystem is what makes it possible. The interesting part is just how much reverse engineering was required:
• Cortex-M3 co-processor + firmware loading
• 16 MiB temporary MMIO window
• DART IOMMU and DMA restrictions
• CD321x / Type-C PHY sequencing
• Changes to the Linux Thunderbolt core

The initial implementation supports USB3-via-USB4 and XDomain, while PCIe and DisplayPort tunneling are still missing.