Reference :https://openwrt.org/docs/guide-developer/build-system/use-patches-with-buildsystem
example:
in the kernel top-level directory
# quilt new platform/913-MIPS-ath79-CUS531MP3-NAND-support-01-change-default-watchdog-timeout.patch
# quilt edit drivers/watchdog/ath79_wdt.c
# quilt diff
--- a/drivers/watchdog/ath79_wdt.c
+++ b/drivers/watchdog/ath79_wdt.c
@@ -38,7 +38,7 @@
#define DRIVER_NAME "ath79-wdt"
-#define WDT_TIMEOUT 15 /* seconds */
+#define WDT_TIMEOUT 60 /* seconds */
#define WDOG_REG_CTRL 0x00
#define WDOG_REG_TIMER 0x040
//generate patches file
# quilt refresh