timer: renesas: Add RZ/A1 R7S72100 OSTM timer driver

Add OSTM timer driver for RZ/A1 SoC. The IP is very different
from the R-Car Gen2/Gen3 one already present in the tree, hence
a custom driver.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Chris Brandt <chris.brandt@renesas.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
index df37a79..5f4bc6e 100644
--- a/drivers/timer/Kconfig
+++ b/drivers/timer/Kconfig
@@ -110,6 +110,13 @@
 	  Select this to enable support for the timer found on
 	  devices based on the MPC83xx family of SoCs.
 
+config RENESAS_OSTM_TIMER
+	bool "Renesas RZ/A1 R7S72100 OSTM Timer"
+	depends on TIMER
+	help
+	  Enables support for the Renesas OSTM Timer driver.
+	  This timer is present on Renesas RZ/A1 R7S72100 SoCs.
+
 config X86_TSC_TIMER_EARLY_FREQ
 	int "x86 TSC timer frequency in MHz when used as the early timer"
 	depends on X86_TSC_TIMER