Add a driver for the SiFive implementation of the RISC-V Platform Level
Interrupt Controller (PLIC). The PLIC connects global interrupt sources
to the local interrupt controller on each hart.
This driver is based on the driver in the RISC-V tree from Palmer Dabbelt,
but has been almost entirely rewritten since, and includes many fixes
from Atish Patra.
Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Atish Patra <atish.patra@wdc.com>
[Binding update by Palmer] Signed-off-by: Palmer Dabbelt <palmer@sifive.com>