[$] A new API for interrupt-aware spinlocks

Boqun Feng spoke atKangrejos2025 about adding a frequently needed API for Rust driversthat need to handle interrupts: interrupt-aware spinlocks. Most drivers willneed to communicate information from interrupt handlers to main driver code, andthis exchange is frequently synchronized with the use of spinlocks. While hisfirst attempts ran into problems, Feng's ultimate solution could help prevent bugsin C code as well, by tracking the number of nested scopes that have disabledinterrupts. The patch set, which contains work from Feng and Lyude Paul, is still under review.