You can check this Hardware design guide for PSoC3-
You can also check the CY8CKIT-030 kit schematics for reference available at this link-
In my opinion this is a not an appropriate answer as this question is very specific and consideres design rules. As mentioned i need simply a hint if VSSD is to be considered as digital ground or ground for power src. of VDDIO which may be either analog or digitial. Hence question is if it is considered a good design if VSSD is connected to analog ground or not.
Pls. try to answer this specific question, I'm familiar with most of application notes and dev-kits for PSOC3.
You need not to create separate Analog ground for VDDA, that is what generally done in Cypress PSoC dev kits, thus I given you the link for our dev kit, where you can even get gerber files for the dev kit.
Thanks & Regards