[poky] Include already exisiting rpm or .spec

[Patrick]

Dear all,

We have some software that we develop from a while that we release as 
rpm. To build these rpm we have some complexe .spec files.

Now we use Yocto/Poky to build many new elements and I would like to 
include in my rootfs generated with Yocto/Poky some of our "old" 
software. We don't want to manage the bitbake recipes and the .spec for 
each of our "old" software.

I then would like to know if I could made a simple bitbake recipes that 
"call/include/use" the .specs files ?
Another solution would be to include directly the rpm to the final 
image. Do you think that it's possible ?

Thanks in advance for idea or hint

Patrick