fix(doc): add note regarding to MMIO mapping

Signed-off-by: Diogo Costa <[email protected]>

source/bao_hyp/config.rst

@@ -483,6 +483,16 @@ where:
     - ``iommu.fq_irq_id`` [mandatory if IOMMU is available] - the Fault Queue interrupt ID (the
       current implementation assumes this is a wired interrupt);
 
+.. note::
+
+   When mapping MMIO regions for guests, the memory regions associated with the GIC (Generic
+   Interrupt Controller) must be excluded. Mapping these regions can lead to conflicts or incorrect
+   behavior, as they are typically managed by Bao through trap-and-emulate mechanisms.
+
+   For instance, if a large MMIO range includes the GIC, the range should be split to create a
+   "hole" for the GIC. This ensures that GIC memory regions (or their equivalents in other
+   architectures, such as RISC-V) are not directly mapped into the guest's virtual address space.
+
 CPU Affinity
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