CrazyHamSales, It does appear that the R210 does support port multipliers, as seen on both buses below. Hope that clarifies the question, as well as provides the specs you are looking for. 
Does anyone know if the R210, the first one not the R210 II, supports port multipliers on the eSata port?  Or any of its Sata ports???? I can't find any mention of the eSata port in any of the manuals or specs online and nobody seems to know what it supports.I have a JBOD with eSata port multiplier that i would like to use to expand out to an additional four drives off the eSata port.  Unfortunately i can't install a eSata host card because the only PCIe slot is already in use running a Perc 6/e for an MD1000. Thanks!
Poweredge R210 eSata, Support Port Multipliers??