I have the same setting as yours.
I use Altium Designer for hardware circuitry and PCB design. But I also have the source firmware files and related utilities. And I have mechanical design files.
Here is how I do it:
Project Name
Firmware
MainCpu
trunk
tags
branches
IoCpu
trunk
tags
branches
Hardware
MainPcb
trunk
tags
branches
IoPcb
trunk
tags
branches
PowerPcb
trunk
tags
branches
Mechanical
Chassis
trunk
tags
branches
Other
trunk
tags
branches
, SVN. , , , FW/HW/MEK. FW/HW/MEK.
FW/HW/MEK , .