hw/riscv: microchip_pfsoc: Document where to look at the SoC memory maps

It is not easy to find out the memory map for a specific component
in the PolarFire SoC as the information is scattered in different
documents. Add some comments so that people can know where to get
such information from the Microchip website.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 1603863010-15807-2-git-send-email-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/microchip_pfsoc.c

@@ -66,6 +66,24 @@
 /* GEM version */
 #define GEM_REVISION    0x0107010c
 
+/*
+ * The complete description of the whole PolarFire SoC memory map is scattered
+ * in different documents. There are several places to look at for memory maps:
+ *
+ * 1 Chapter 11 "MSS Memory Map", in the doc "UG0880: PolarFire SoC FPGA
+ *   Microprocessor Subsystem (MSS) User Guide", which can be downloaded from
+ *   https://www.microsemi.com/document-portal/doc_download/
+ *   1244570-ug0880-polarfire-soc-fpga-microprocessor-subsystem-mss-user-guide,
+ *   describes the whole picture of the PolarFire SoC memory map.
+ *
+ * 2 A zip file for PolarFire soC memory map, which can be downloaded from
+ *   https://www.microsemi.com/document-portal/doc_download/
+ *   1244581-polarfire-soc-register-map, contains the following 2 major parts:
+ *   - Register Map/PF_SoC_RegMap_V1_1/pfsoc_regmap.htm
+ *     describes the complete integrated peripherals memory map
+ *   - Register Map/PF_SoC_RegMap_V1_1/MPFS250T/mpfs250t_ioscb_memmap_dri.htm
+ *     describes the complete IOSCB modules memory maps
+ */
 static const struct MemmapEntry {
     hwaddr base;
     hwaddr size;