The rapid growth of non-terrestrial communication necessitates its integration with existing Terrestrial Network (TN), as highlighted in 3GPP Releases 16 and 17. To manage this complex structure effectively, the adoption of a Radio Access Network (RAN) architecture with Functional Split (FS) offers advantages in flexibility, scalability, and cost-efficiency. RAN achieves this by disaggregation of functionalities into three separate units. Analogous to the TN approach, 3GPP is extending this concept to non-terrestrial platforms as well. This work presents a general analysis of the requested Fronthaul (FH) data rate on the feeder link between a non-terrestrial platform and the ground-station for Uplink (UL) communication. The derived calculations are exemplarily evaluated using common system parameters for two typical non-terrestrial communication platforms, the Low Earth Orbit (LEO) satellites and the High Altitude Platform Station (HAPS). In addition to the fulfillment of Timing requirements, computational complexity and on board of flying nodes, the calculated FH data rate will be an important factor for choosing the actual functional split per scenario.