https://msdn.microsoft.com/en-us/library/windows/hardware/dn915086(v=vs.85).aspx
Existing Windows Phones that include the SoCs listed in Table 6 can be updated to Windows 10 Mobile.
Table 6: SoCs supported in Windows Phones that can be updated to Windows 10 Mobile
Manufacturer SoC
Qualcomm Technologies, Inc.
MSM8x10, MSM8x12, MSM8x26, MSM8916, MSM8926, MSM8x28, MSM8928, MSM8974, MSM8974Pro, MSM8960, MSM8260A, MSM8660A, MSM8930AA, MSM8930AB, MSM8630, MSM8230, MSM8627, MSM8227, MSM8994, MSM8992, MSM8952, MSM8909, MSM8208