risc-v: clarify PLIC is for SiFive U54/U74

RISC-V defines the concept of a PLIC, but leaves the details open. The
driver is for the PLIC of the SiFive U54/U74 SOC, which is used on
the HiFive Unleashed/Unmatched and Polarfire board.

Signed-off-by: Axel Heider <axel.heider@hensoldt-cyber.de>

include/drivers/irq/riscv_plic0.h

@@ -3,10 +3,18 @@
  * Copyright 2021, HENSOLDT Cyber
  *
  * SPDX-License-Identifier: GPL-2.0-only
+ *
+ * SiFive U54/U74 PLIC handling (HiFive Unleashed/Unmatched, Polarfire)
  */
 
 #pragma once
 
+/* This is a check that prevents using this driver blindly. Extend the list if
+ * this driver is confirmed to be working on other platforms. */
+#if !defined(CONFIG_PLAT_HIFIVE) && !defined(CONFIG_PLAT_POLARFIRE)
+#error "This code supports the SiFive U54/U74 PLIC only."
+#endif
+
 /* tell the kernel we have the set trigger feature */
 #define HAVE_SET_TRIGGER 1
 

tools/hardware.yml

@@ -249,7 +249,7 @@ devices:
         user: true
         kernel_size: 0x1000
 
-  # RISC-V PLIC
+  # SiFive U54/U74 PLIC (HiFive, Polarfire)
   - compatible:
       - riscv,plic0
     regions: