After 10 seconds RTC Wakeup via PMIC RTC.
Linux command: 
echo 1 > /sys/kernel/debug/pm_debug/enable_off_mode;
echo enabled > /sys/class/rtc/rtc1/device/power/wakeup;
rtcwake -d /dev/rtc1 -m mem -s 10

PMIC TPS65910 @ I2C address 0x2d
U-Boot# i2c md 0x2d 0x0.1 0x80
0000: 33 02 00 01 01 00 00 00 00 01 00 01 01 00 00 00    3...............
0010: 01 c2 08 00 00 27 00 00 00 00 00 00 9f 0d 09 00    .....'..........
0020: 01 0d 2b 00 05 2b 00 04 00 00 00 00 00 00 00 00    ..+..+..........
0030: 09 0d 01 0d 0d 0d 09 01 0d 00 00 00 00 00 3b 14    ..............;.
0040: 35 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    5...............
0050: 40 bf 00 03 00 00 00 00 00 00 00 00 00 00 00 00    @...............
0060: 0a 0a 0a 0a 0a 0a 00 00 00 00 00 00 00 00 00 00    ................
0070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

AM3352 RTCSS Registers
U-Boot# md.l 0x44e3e000 0x40
44e3e000: 00000042 00000002 00000000 00000001    B...............
44e3e010: 00000001 00000000 00000000 00000000    ................
44e3e020: 00000020 00000000 00000000 00000001     ...............
44e3e030: 00000001 00000002 00000000 00000000    ................
44e3e040: 00000001 00000082 00000010 00000000    ................
44e3e050: 00000040 00000048 00000000 00000000    @...H...........
44e3e060: 80991f0c 33548cd0 00000800 00000800    ......T3........
44e3e070: 00000800 4eb01106 00000003 00000000    .......N........
44e3e080: 00000050 00000000 00000000 00000001    P...............
44e3e090: 00000001 00000000 00030004 00000000    ................
44e3e0a0: 00000000 00000000 00000000 00000000    ................
44e3e0b0: 00000000 00000000 00000000 00000000    ................
44e3e0c0: 00000000 00000000 00000000 00000000    ................
44e3e0d0: 00000000 00000000 00000000 00000000    ................
44e3e0e0: 00000000 00000000 00000000 00000000    ................
44e3e0f0: 00000000 00000000 00000000 00000000    ................
U-Boot# mw.l 0x44e3e098 0	# Clear RTC_PMIC.PWR_ENABLE_EN
U-Boot# md.l 0x44e3e098 1
44e3e098: 00020000		# Pin PMIC_POWER_EN still low
U-Boot# mw.l 0x44e3e044 0x80	# Clear ALARM2 interrupt status
U-Boot# md.l 0x44e3e044 1
44e3e044: 00000002		# Pin PMIC_POWER_EN still low
U-Boot# i2c mw 0x2d 0x3f.1 0x10	# Release PMIC Bit DEV_ON
-> Device shuts down