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 

iface eth0 inet static 
address 192.168.0.101
netmask 255.255.255.0 

Both failed. Where do I go?