Document splitting is part of New GL PCA.

As per New GL PCA there are two entry views one for Entry 
view and General Ledger view. In General Ledger view you 
can find the document splitting.

For example
Material purchased for two differant profit centers under 
One Invoice. 

Entry view
Expenses    Dr  100 Profit center 1
Expemses    Dr  100 Profit center 2
To
Vendor      Cr  200

General Ledger View
Expenses    Dr 100 Profit center 1
Expenses    Dr 100 Profit center 2
To
Payable     Cr 100 Profit center 1
Payable     Cr 100 Profit center 2

If you see the general ledger view you can find the object 
of document splitting. 

Under Business Area concept you can not find this facility

Hope this will clarify