This patch adds support for threaded IRQs and handlers through
irq::ThreadedRegistration and the irq::ThreadedHandler trait.

Threaded interrupts are more permissive in the sense that further
processing is possible in a kthread. This means that said execution takes
place outside of interrupt context, which is rather restrictive in many
ways.

Registering a threaded irq is dependent upon having an IrqRequest that
was previously allocated by a given device. This will be introduced in
subsequent patches.

Tested-by: Joel Fernandes <joelagnelf@nvidia.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250811-topics-tyr-request_irq2-v9-4-0485dcd9bcbf@collabora.com
[ Add now available intra-doc links back in. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

This patch adds support for non-threaded IRQs and handlers through
irq::Registration and the irq::Handler trait.

Registering an irq is dependent upon having a IrqRequest that was
previously allocated by a given device. This will be introduced in
subsequent patches.

Tested-by: Joel Fernandes <joelagnelf@nvidia.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250811-topics-tyr-request_irq2-v9-3-0485dcd9bcbf@collabora.com
[ Remove expect(dead_code) from Flags::into_inner(), add
  expect(dead_code) to IrqRequest::new(), fix intra-doc links. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Manipulating IRQ flags (i.e.: IRQF_*) will soon be necessary, specially to
register IRQ handlers through bindings::request_irq().

Add a kernel::irq::Flags for that purpose.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Joel Fernandes <joelagnelf@nvidia.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250811-topics-tyr-request_irq2-v9-2-0485dcd9bcbf@collabora.com
[ Use expect(dead_code) for into_inner(), fix broken intra-doc link and
  typo. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Add the IRQ module. Future patches will then introduce support for IRQ
registrations and handlers.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Joel Fernandes <joelagnelf@nvidia.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250811-topics-tyr-request_irq2-v9-1-0485dcd9bcbf@collabora.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>