For anyone who is interested in being able to run openSUSE 12.3 on Globalscale's Mirabox. Unfortunately I did not succeed...
First I tried with the "standard" mirabox kernel 184.108.40.206 and the rootfs for openSUSE 12.3 for armv7 (see my previous post on http://www.newit.co.uk/forum/index.php/topic,3953.msg10562.html). That did not work since (as I learned from some people around here, thanks!) the kernel was too old for openSUSE. So I tried to compile my own kernel.
I started with 3.9-rc5 and a while later with 3.9-rc6. I did quite some tweaks and twiddeling and finally came up with this kernel config: http://pastebin.com/MjpE3yUD. This one does run, you can get into openSUSE, login as root etc., but I wasn't able to get the network up and running and the USB3 ports working. Note that my config file disables wifi and bluetooth (I got some errors and since I do not need it I disabled them).
For the network, for 3.9-rc6 it seems to run but it cannot connect to "the outside world" even when I give it a fixed ip address with ifconfig (it is not able to get an ip address from my dhcp server). The weird thing is that the MAC addresses openSUSE thinks it has for eth0 and eth1 are not the MAC addresses which are printed on the mirabox itself.
For the USB3 ports, I have no clue at all how to get those working. What I know, is that they are connected to an internal PCIe interface, but I couldn't find any options to enable it. For me, the USB3 ports are fundamental since I need to connect an external hard disk to it. I know it can be done because I have them working using debian 6 (with the "standard" mirabox kernel 220.127.116.11).
For anyone who wants to compile the kernel, be aware it works with a device tree. Since Mirabox u-boot is quite old, you cannot use it directly. This is what I did to get a working uImage:
cp arch/arm/boot/zImage .
cp arch/arm/boot/dts/armada-370-mirabox.dtb .
cat zImage armada-370-mirabox.dtb > zImage-mirabox
mkimage -A arm -O linux -T kernel -C none -a 0x00008000 -e 0x00008000 -n linux-3.9-rc6 -d zImage-mirabox uImage
If anyone wants to proceed with this, please feel free to do so! And please post your findings back here.