/sys/kernel/debug/irq_domain_mapping is a pretty useful tool to find out how irqdomains (and individual interrupts) are setup, but it lacks an understanding of hierarchical domains, and is not documented at all.
Let's start to remedy this, as people seem incredibly puzzled by the whole stacked domain thing, wasting too much time reverse-engineering the core code while just peeking at a debugfs file could give them an insight on what's going on. Marc Zyngier (4): irqdomain: Let irq_domain_mapping display hierarchical domains irqdomain: Let irq_domain_mapping display ACPI fwnode attributes genirq/msi: Populate the domain name if provided by the irqchip Documentation: Update IRQ-domain.txt to document irq_domain_mapping Documentation/IRQ-domain.txt | 41 ++++++++++++++++++++-- kernel/irq/irqdomain.c | 81 ++++++++++++++++++++++++++++++-------------- kernel/irq/msi.c | 10 ++++-- 3 files changed, 102 insertions(+), 30 deletions(-) -- 2.11.0