[libgpiod][PATCH 2/2] README: mention the linux v5.10 requirement for libgpiod v2

[Bartosz Golaszewski <brgl@xxxxxxxx>]

From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

Major version 2 of libgpiod requires linux kernel uAPI v2 to be available.
This was released in linux v5.10 so mention it in the README.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
 README | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/README b/README
index 632aab3..7680915 100644
--- a/README
+++ b/README
@@ -8,8 +8,10 @@ libgpiod
              character device (gpiod stands for GPIO device)
 
 Since linux 4.8 the GPIO sysfs interface is deprecated. User space should use
-the character device instead. This library encapsulates the ioctl calls and
-data structures behind a straightforward API.
+the character device instead. Version 2 of libgpiod requires the new GPIO
+character device uAPI to be available which was first released in linux v5.10.
+This library encapsulates the ioctl calls and data structures behind a
+straightforward API.
 
 RATIONALE
 ---------
-- 
2.40.1