Process isolation of drivers is just not very useful when the driver is interfacing with a device that has full access to system memory. Which is the case for many devices today unless you use IOMMU to prevent this.
https://docs.sel4.systems/projects/sel4/frequently-asked-que...
This is all essential trust anyways. The leaps and bounds we've achieved through hardware engineering have the burden that they aren't credible for security. You can use IOMMU, but perhaps I won't. Integrated co-development of hardware and software is ideal, but generally there is an adversarial relationship, and we must reflect that in the software. Trust and security are not yes/no questions. We have to keep pushing boundaries. seL4 is a good start; let's make more from it.