docs: Document the RX target

Add rx-virt target specification document.

Signed-off-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Message-Id: <20200308130637.37651-1-ysato@users.sourceforge.jp>
[PMD: Cover in MAINTAINERS, rename as gdbsim, use machine argument]
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

MAINTAINERS

@@ -1261,6 +1261,7 @@ RX Machines
 rx-gdbsim
 M: Yoshinori Sato <ysato@users.sourceforge.jp>
 S: Maintained
+F: docs/system/target-rx.rst
 F: hw/rx/rx-gdbsim.c
 F: tests/acceptance/machine_rx_gdbsim.py
 

docs/system/target-rx.rst

@@ -0,0 +1,36 @@
+.. _RX-System-emulator:
+
+RX System emulator
+--------------------
+
+Use the executable ``qemu-system-rx`` to simulate RX target (GDB simulator).
+This target emulated following devices.
+
+-  R5F562N8 MCU
+
+   -  On-chip memory (ROM 512KB, RAM 96KB)
+   -  Interrupt Control Unit (ICUa)
+   -  8Bit Timer x 1CH (TMR0,1)
+   -  Compare Match Timer x 2CH (CMT0,1)
+   -  Serial Communication Interface x 1CH (SCI0)
+
+-  External memory 16MByte
+
+Example of ``qemu-system-rx`` usage for RX is shown below:
+
+Download ``<u-boot_image_file>`` from
+https://osdn.net/users/ysato/pf/qemu/dl/u-boot.bin.gz
+
+Start emulation of rx-virt::
+  qemu-system-rx -M gdbsim-r5f562n8 -bios <u-boot_image_file>
+
+Download ``kernel_image_file`` from
+https://osdn.net/users/ysato/pf/qemu/dl/zImage
+
+Download ``device_tree_blob`` from
+https://osdn.net/users/ysato/pf/qemu/dl/rx-virt.dtb
+
+Start emulation of rx-virt::
+  qemu-system-rx -M gdbsim-r5f562n8 \
+      -kernel <kernel_image_file> -dtb <device_tree_blob> \
+      -append "earlycon"

docs/system/targets.rst

@@ -18,3 +18,4 @@ Contents:
    target-m68k
    target-xtensa
    target-s390x
+   target-rx