音频设备列表中0 1 7三个设备分别代表什么？

Chip Platform Rockchip
1 
/ # cat /proc/asound/cards
 0 [rockchiprk3308v]: rockchip_rk3308 - rockchip,rk3308-vad
                      rockchip,rk3308-vad
 1 [rockchiprk3308p]: rockchip_rk3308 - rockchip,rk3308-pcm
                      rockchip,rk3308-pcm
 7 [Loopback       ]: Loopback - Loopback
                      Loopback 1
/ # arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: rockchiprk3308v [rockchip,rk3308-vad], device 0: dailink-multicodecs multicodec-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: rockchiprk3308p [rockchip,rk3308-pcm], device 0: dailink-multicodecs dummy_codec-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 7: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 7: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 7/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
2

声卡0 用于lineout 和耳机输出，同时也通过该声卡录制8通道的模拟Mic 输入，这样理解对吗？？？？
arecord 录音时指定的hw:0,0 是通过麦克风阵列选择不同通道进行录音的吗？？？？
声卡1 和7 loopback又有什么作用呢？？？

3

根据rk3308-firefly.dtsi和rk3308-roc-cc-dmic-pdm_emmc.dts的描述
声卡0 是数字麦克阵列
声卡1 是蓝牙
声卡7 是回采