Documentation: Add Rotundu

Add information about flash and programming header.

Change-Id: If34016e20dd580f92695bef5b67dd0c282b0b421
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32894
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

Documentation/mainboard/index.md

@@ -44,6 +44,7 @@ The boards in this section are not real mainboards, but emulators.
 ## Open Cellular
 
 - [Elgon](opencellular/elgon.md)
+- [Rotundu](opencellular/rotundu.md)
 
 ## HP
 

Documentation/mainboard/opencellular/rotundu.md

@@ -0,0 +1,76 @@
+# Rutundu
+
+This page describes how to run coreboot on the [Rotundu] compute board
+from [OpenCellular].
+
+## TODO
+
+* Configure UART
+* EC interface
+
+## Flashing coreboot
+
+```eval_rst
++---------------------+------------+
+| Type                | Value      |
++=====================+============+
+| Socketed flash      | no         |
++---------------------+------------+
+| Model               | W25Q128    |
++---------------------+------------+
+| Size                | 16 MiB     |
++---------------------+------------+
+| In circuit flashing | yes        |
++---------------------+------------+
+| Package             | SOIC-8     |
++---------------------+------------+
+| Write protection    | No         |
++---------------------+------------+
+| Dual BIOS feature   | No         |
++---------------------+------------+
+| Internal flashing   | yes        |
++---------------------+------------+
+```
+
+### Internal programming
+
+The SPI flash can be accessed using [flashrom].
+
+### External programming
+
+The GBCv1 board does have a pinheader to flash the SOIC-8 in circuit.
+Directly connecting a Pomona test-clip on the flash is also possible.
+
+**Closeup view of SOIC-8 flash IC**
+
+![][rotundu_flash]
+
+[rotundu_flash]: rotundu_flash.jpg
+
+**SPI header**
+
+![][rotundu_header2]
+
+[rotundu_header2]: rotundu_header2.jpg
+
+**SPI header pinout**
+
+Dediprog compatible pinout.
+
+![][rotundu_j16]
+
+[rotundu_j16]: rotundu_j16.png
+
+## Technology
+
+```eval_rst
++------------------+--------------------------------------------------+
+| SoC              | Intel Baytrail                                   |
++------------------+--------------------------------------------------+
+| Coprocessor      | Intel ME                                         |
++------------------+--------------------------------------------------+
+```
+
+[Rotundu]: https://github.com/Telecominfraproject/OpenCellular
+[OpenCellular]: https://code.fb.com/connectivity/introducing-opencellular-an-open-source-wireless-access-platform/
+[flashrom]: https://flashrom.org/Flashrom