This PR adds support for PINE64 Star64 64-bit RISC-V SBC, based on StarFive JH7110 SoC. Most of the code is derived from NuttX for QEMU RISC-V (Kernel Mode). [The source files are explained in the articles here](https://github.com/lupyuen/nuttx-star64)
Modified Files:
boards/Kconfig: Added Star64 board
New Files in boards/risc-v/jh7110/star64:
src/jh7110_appinit.c: Startup Code
include/board.h: Star64 Definitions
include/board_memorymap.h: Memory Map
src/etc/init.d/rc.sysinit, rcS: Startup Script
src/.gitignore: Ignore the tmp filesystem
scripts/ld.script: Linker Script
scripts/Make.defs: Star64 Makefile
src/Makefile: Star64 Makefile
Kconfig: Star64 Config
configs/nsh/defconfig: NSH Build Config
Updated Documentation:
introduction/detailed_support.rst: Added StarFive JH7110 SoC and Star64 SBC
platforms/risc-v/jh7110/index.rst: New page for StarFive JH7110 SoC
platforms/risc-v/jh7110/boards/star64/index.rst: Building and booting NuttX for Star64
