qemu-doc: Add nanoMIPS ISA information

Add nanoMIPS information in qemu-doc.texi. An example of usage
is included.

Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: Stefan Markovic <smarkovic@wavecomp.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>

qemu-doc.texi

@@ -1995,6 +1995,10 @@ Set the emulated machine type. The default is sun4u.
 @section MIPS System emulator
 @cindex system emulation (MIPS)
 
+@menu
+* nanoMIPS System emulator ::
+@end menu
+
 Four executables cover simulation of 32 and 64-bit MIPS systems in
 both endian options, @file{qemu-system-mips}, @file{qemu-system-mipsel}
 @file{qemu-system-mips64} and @file{qemu-system-mips64el}.
@@ -2086,6 +2090,31 @@ SCSI controller
 G364 framebuffer
 @end itemize
 
+@node nanoMIPS System emulator
+@subsection nanoMIPS System emulator
+@cindex system emulation (nanoMIPS)
+
+Executable @file{qemu-system-mipsel} also covers simulation of
+32-bit nanoMIPS system in little endian mode:
+
+@itemize @minus
+@item
+nanoMIPS I7200 CPU
+@end itemize
+
+Example of @file{qemu-system-mipsel} usage for nanoMIPS is shown below:
+
+Download @code{<disk_image_file>} from @url{https://mipsdistros.mips.com/LinuxDistro/nanomips/buildroot/index.html}.
+
+Download @code{<kernel_image_file>} from @url{https://mipsdistros.mips.com/LinuxDistro/nanomips/kernels/v4.15.18-432-gb2eb9a8b07a1-20180627102142/index.html}.
+
+Start system emulation of Malta board with nanoMIPS I7200 CPU:
+@example
+qemu-system-mipsel -cpu I7200 -kernel @code{<kernel_image_file>} \
+    -M malta -serial stdio -m @code{<memory_size>} -hda @code{<disk_image_file>} \
+    -append "mem=256m@@0x0 rw console=ttyS0 vga=cirrus vesa=0x111 root=/dev/sda"
+@end example
+
 
 @node ARM System emulator
 @section ARM System emulator