Reg SoC Example without using Linux

I'm assuming you're interested in baremetal rather than Zephyr. 

There is no other "full-on" reference designs other than Hello World example as far as I know. But, the example includes all the necessary peripherals (UART, I2C, SPIO, GPIO, etc.).  Take a look at the included and source folders in the Github repo https://github.com/altera-fpga/baremetal-drivers

For Cyclone V, take a look at the AN 709: HPS SoC Boot Guide - Cyclone V SoC Development Kit. This devkit comes with a project/software that you can run baremetal. 

https://docs.altera.com/r/docs/683265/current/an-709-hps-soc-boot-guide-cyclone-v-soc-development-kit/an-709-hps-soc-boot-guide-cyclone-v-soc-development-kit

https://www.rocketboards.org/foswiki/Documentation/HWLib

https://www.rocketboards.org/foswiki/Documentation/BuildingBootloaderCycloneVAndArria10#U_45Boot_Examples

There are also a healthy amount of third-party reference designs you can find online. Take a look at one from Cornell University below it goes through Cyclone V HPS baremetal. I'd look at Cornell's ECE5760 Course page. They do a lot of stuff with DE1-SoC and DE10-Nano boards. It's all available online.

https://people.ece.cornell.edu/land/courses/ece5760/DE1_SOC/SoC-FPGA%20Design%20Guide_EPFL.pdf