Quick answer: NO

Long Answer: Really, you cant. if you hope to plug in something in the micro usb receptacle, it works as client only, sorry

Hope Answer: Today, Host Mode is just a dream. The OTG team woking in the OTG thread isnt in a stable place yet, and even that, asking for the appropiate kernel module for your specific usb-rs232 adapter is waaaaaaaaaaaay early. so going this way is a long ahot only

Hope this helps