mb/up/squared: Add mainboard

Works:
- bootblock, romstage, ramstage
- Serial console UART0, UART1
- SPI flash console
- iGPU init with libgfxinit
- LAN1, LAN2
- USB2, USB3
- HDMI, DisplayPort
- eMMC
- flashing with flashrom externally

WIP:
- Documentation
- VGA
    For some reason Seabios can not find the CBFS region
    and therefore it can't load seavgabios, but generally
    it is working as soon as Linux is booted.
- ACPI

Works not:
- Devices needs proper configuration
- Seabios can't find CBFS region

Untested:
- GPIO pin header
- 60 pin EXHAT
- Camera interface
  - MIPI-CSI2 2-lane (2MP)
  - MIPI-CSI2 4-lane (8MP)
- SATA3
- USB3 OTG
- embedded DisplayPort
- M.2 slot
- mini PCIe
- flashing with flashrom internally using Linux

Change-Id: Ia913534ec176fc600fcd4ce3af335ebe682b0ed4
Signed-off-by: Felix Singer <felix.singer@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31378
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

Documentation/mainboard/index.md

@@ -82,3 +82,7 @@ The boards in this section are not real mainboards, but emulators.
 ## Supermicro
 
 - [X10SLM+-F](supermicro/x10slm-f.md)
+
+## UP
+
+- [Squared](up/squared/index.md)

Documentation/mainboard/up/squared/index.md

@@ -0,0 +1,99 @@
+# Squared
+
+## Overview
+### Top
+![][overview_top]
+
+### Bottom
+![][overview_bottom]
+
+## Mainboard components
+### Platform
+```eval_rst
++------------------+----------------------------------+
+| CPU              | Intel Atom, Celeron, Pentium     |
++------------------+----------------------------------+
+| PCH              | Intel Apollo Lake                |
++------------------+----------------------------------+
+| EC / Super IO    | N/A                              |
++------------------+----------------------------------+
+| Coprocessor      | Intel TXE 3.0                    |
++------------------+----------------------------------+
+```
+
+### Flash chip
+```eval_rst
++---------------------+------------+
+| Type                | Value      |
++=====================+============+
+| Socketed flash      | no         |
++---------------------+------------+
+| Vendor              | Winbond    |
++---------------------+------------+
+| Model               | W25Q128FW  |
++---------------------+------------+
+| Voltage             | 1.8V       |
++---------------------+------------+
+| Size                | 16 MiB     |
++---------------------+------------+
+| Package             | SOIC-8     |
++---------------------+------------+
+| Write protection    | No         |
++---------------------+------------+
+| Internal flashing   | No         |
++---------------------+------------+
+| In curcuit flashing | Yes        |
++---------------------+------------+
+```
+
+## Board status
+### Working
+- bootblock, romstage, ramstage
+- Serial console UART0, UART1
+- SPI flash console
+- iGPU init with libgfxinit
+- LAN1, LAN2
+- USB2, USB3
+- HDMI, DisplayPort
+- eMMC
+- flashing with flashrom externally
+
+### Work in progress
+- Documentation
+- ACPI
+
+### Not working / Known issues
+- Generally SeaBIOS works, but it can't find the CBFS region and therefore it can't load seavgabios. This is because of changes at the Apollolake platform.
+
+### Untested
+- GPIO pin header
+- 60 pin EXHAT
+- Camera interface
+  - MIPI-CSI2 2-lane (2MP)
+  - MIPI-CSI2 4-lane (8MP)
+- SATA3
+- USB3 OTG
+- embedded DisplayPort
+- M.2 slot
+- mini PCIe
+- flashing with flashrom internally using Linux
+
+## Building and flashing coreboot
+### Building
+
+```bash
+make distclean
+touch .config
+./util/scripts/config --enable VENDOR_UP
+./util/scripts/config --enable BOARD_UP_SQUARED
+./util/scripts/config --enable NEED_IFWI
+./util/scripts/config --enable HAVE_IFD_BIN
+./util/scripts/config --set-str IFWI_FILE_NAME "<path_to_your_bios_region>"
+./util/scripts/config --set-str IFD_BIN_PATH "<path_to_your_ifd_region>"
+make olddefconfig
+```
+
+### Flashing
+
+[overview_top]: top.jpg
+[overview_bottom]: bottom.jpg