Is Irda a chipset chip? (for instance, belongs to Intel ICH?)
a third part vendor device? 
IrDA is a standard spec, see
It is typically a third party device on your average laptop but I think there are
integrated chipset versions as well. 
where can i find a specification for the device? 
Which device? Typically from the manufacturers homepage... 
How can i totally shutdown the Irda device so it consumes 0(zero) power? 
This depends on the hardware, there is no generic way apart from not loading
the kernel module for it, which most certainly turns it on.