[$] A new API for interrupt-aware spinlocks

Boqun Feng spoke at

Kangrejos 2025 about adding a frequently needed API for Rust drivers
that need to handle interrupts: interrupt-aware spinlocks. Most drivers will
need to communicate information from interrupt handlers to main driver code, and
this exchange is frequently synchronized with the use of spinlocks. While his
first attempts ran into problems, Feng's ultimate solution could help prevent bugs
in C code as well, by tracking the number of nested scopes that have disabled
interrupts. The
patch set, which contains work from Feng and Lyude Paul, is still under review.