Add inherited interrupt-parent lookup

[ZR233]

Summary

• add inherited interrupt-parent lookup for fdt-edit node views and typed nodes
• carry interrupt-parent through fdt-raw inherited node context
• add regression tests for inherited lookup and local override behavior

Testing

• cargo test -p fdt-raw
• cargo test -p fdt-edit --test clock --test encode --test fdt --test pci --test range

Closes #8

[Copilot]

Pull request overview

Adds support for inheriting the interrupt-parent property up the device tree hierarchy, aligning behavior with the DT spec and exposing the effective value through both fdt-raw node iteration context and fdt-edit node views/typed nodes.

Changes:

• Implement inherited interrupt-parent resolution in fdt-raw nodes via an inherited NodeContext field plus a new NodeBase::interrupt_parent() accessor.
• Carry the effective interrupt-parent through fdt-raw iteration so descendants can resolve it without re-walking ancestors.
• Add regression tests in both crates to validate inheritance and local override behavior.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
fdt-raw/tests/node.rs	Adds regression test ensuring /chosen inherits interrupt-parent from /.
fdt-raw/src/node/mod.rs	Extends inherited node context with interrupt_parent and adds effective lookup API.
fdt-raw/src/iter.rs	Propagates effective interrupt-parent through the iterator’s context stack.
fdt-edit/tests/fdt.rs	Adds inheritance + override test for NodeView/typed node accessors.
fdt-edit/src/node/view/mod.rs	Implements NodeView::interrupt_parent() (ancestor walk) and exposes via NodeType.
fdt-edit/src/node/view/generic.rs	Exposes interrupt_parent() on the generic node view wrapper.
fdt-edit/src/node/mod.rs	Clarifies Node::interrupt_parent() returns only the local property value.

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[Copilot]

In child_context, props.interrupt_parent.or(node.interrupt_parent()) evaluates node.interrupt_parent() eagerly, which re-scans the node’s properties even when props.interrupt_parent is already Some. This can add significant overhead while iterating large trees. Use a lazy alternative (e.g. or_else(|| node.interrupt_parent())) or compute from the already-available inherited context (e.g. props.interrupt_parent.or(self.current_context().interrupt_parent)) to avoid the extra scan.

Suggested change

	.or(node.interrupt_parent()),
	.or_else(|| node.interrupt_parent()),