Hi all,

This is the remaining series for the full functional "dynamic node
programming using overlay dtbo" feature. The first part [1] has
already been merged.

Quoting from the original series, the first part has already made
Xen aware of new device tree node which means updating the dt_host
with overlay node information, and in this series, the goal is to
map IRQ and IOMMU during runtime, where we will do the actual IOMMU
and IRQ mapping and unmapping to a running domain. Also, documentation
of the "dynamic node programming using overlay dtbo" feature is added.

During the discussion in v3, I was recommended to split the overlay
devices attach/detach to/from running domains to separated patches [3].
But I decided to only expose the xl user interfaces together to the
users after device attach/detach is fully functional, so I didn't
split the toolstack patch (#8).

Patch 1 is a fix of the existing code which is noticed during my local
tests, details please see the commit message.

Gitlab CI for this series can be found in [2].

[1] https://lore.kernel.org/xen-devel/20230906011631.30310-1-vikram.garhwal@amd.com/
[2] https://gitlab.com/xen-project/people/henryw/xen/-/pipelines/1301720278
[3] https://lore.kernel.org/xen-devel/e743d3d2-5884-4e55-8627-85985ba339f9@amd.com/


Changes in v5:
- address Julien's comments
- remove patches and mentions of the "detach" operation
- add a check for xen,reg and return error if present

- Stefano