Where do I assign a static IP address to my sole network interface?

I tried using the Linux boot parameters (in extlinux.conf):

LABEL Arria10 SOCDK SDMMC
    KERNEL ../zImage
    FDT ../socfpga_arria10_phead.dtb
    APPEND root=/dev/mmcblk0p2 rw rootwait earlyprintk console=ttyS0,115200n8 ip=192.168.0.101:255.255.255.0:eth0

 

Then I tried editing: /etc/network/interfaces

 

 

Both failed. Where do I go?