Hello Jan,
As your preliminary research has shown, the CC2538 has an ARM core. It uses JTAG for programming. The CC Debugger in its current state is for the somewhat proprietary Chipcon protocol and SPI. You can use the SmartRF06 or an emulator with the CC2538EM for programming.
The CC2538 IDE Guide swru345.pdf explains how the IAR EWARM the Segger J-Link or IAR I-jet emulators can be used as alternatives to XDS100v3. Both will only support 4-pin JTAG. Or the XDS100v3 in CCS.
Also on the CC2538 product page, you can download the CC2538 Foundation software swrc271a.zip. Inside the docs folder you will find more information about programming the device.
Thanks,