[PATCH] docs: Add RX target.

[Yoshinori Sato <ysato@users.sourceforge.jp>]

Add rx-virt target specificaion document.

Signed-off-by: Yoshinori Sato <ysato@users.sourceforge.jp>
---
 docs/system/target-rx.rst | 35 +++++++++++++++++++++++++++++++++++
 docs/system/targets.rst   |  1 +
 2 files changed, 36 insertions(+)
 create mode 100644 docs/system/target-rx.rst

diff --git a/docs/system/target-rx.rst b/docs/system/target-rx.rst
new file mode 100644
index 0000000000..8540fd5218
--- /dev/null
+++ b/docs/system/target-rx.rst
@@ -0,0 +1,35 @@
+.. _RX-System-emulator:
+
+RX System emulator
+--------------------
+
+Use the executable ``qemu-system-rx`` to simulate a Virtual RX target.
+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 -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 -kernel <kernel_image_file> -dtb <device_tree_blob> \
+      -append "earlycon"
diff --git a/docs/system/targets.rst b/docs/system/targets.rst
index eba3111247..946f513daa 100644
--- a/docs/system/targets.rst
+++ b/docs/system/targets.rst
@@ -17,3 +17,4 @@ Contents:
    target-arm
    target-m68k
    target-xtensa
+   target-rx
-- 
2.20.1